Daytime Running Lights: No Statistically Significant Effect On Safety
September 25th, 2008 Posted in Daytime Running Lights, James Baxter
By James Baxter, NMA President
You’re not likely to see any bold headlines, and CNN will not be interviewing Bush administration DOT officials, but the seven year long saga of trying to prove that Daytime Running Lights improve highway safety is coming to a close.
The official results are couched in terms like “not statistically significant,” meaning they don’t prevent crashes or make our highways safer.
The motivation for the study was a General Motors petition to make Daytime Running Lights (DRLs) mandatory on all vehicles sold in the United States. For several years prior to this GM had been fitting its vehicles with DRLs and expected the masses to respond to this patronizing gesture with their checkbooks open.
Instead, random iconoclasts and other non-believers complained about glare, blanked out directional lights, wasted fuel, and just simple irritation with the DRLs concept. They apparently went elsewhere with their checkbooks and bought cars that allowed the operator to decide when to turn the lights off and on.
Two studies preceded this last effort and they indicated some safety benefit attributable to DRLS. However, the DRL critics were just as relentless in pointing out the flaws, and bad assumptions inherent in these studies. The third effort was an attempt to address these earlier failings.
To some degree the last study was an improvement over the prior efforts, but it too failed to address many of the more difficult questions, particularly those questions that suggested DRLS not only did not improve highway safety, rather they detracted from highway safety. Fittingly, the sample population of vehicles investigated in the study were GM products.
Skipping to the final results first, the researchers could find no statistically significant evidence that DRL equipped cars and trucks were less prone to be in accidents where daytime running lights could have been a factor.
Within the study they found random blips where DRL equipped vehicles were disproportionately involved in fewer — or more — accidents than not DRL equipped vehicles. This was largely due to small sub-sample sizes where random variations will cause distortions over short time spans. When the subgroups were combined and the number of sample vehicles increased, the differences between DRL and non-DRL vehicles evaporated.
There were primary and basic assumptions made that may not be valid.
For example, the study design was based on the premise that comparing accident involvement of the two types of vehicles; those equipped with DRLs and those not equipped with DRLs would answer the “safety question.” However, the concerns raised by DRL critics are only peripherally related to actual accident involvement of DRL equipped vehicles. It was their contention that DRL equipped vehicles were causing accidents, even though these same vehicles may not have been involved in the actual accidents.
One such subset of DRL opponents consists of motorcyclists who believe DRL equipped autos and trucks diminished or confused the visibility of motorcycles that typically operate with headlights on during daylight hours. (A Japanese study that explored the effect of daytime headlight use by motorcyclists found no benefit, but that’s another topic.) The correspondingly significant increase in motorcycle accidents has added emphasis to this claim. However, the concurrent increase in motorcycle ownership and use tracks this same increase in motorcycle accidents.
Complaints of “glare,” obscured turn signals, confused distance perception (“is that one headlight close by or two headlights far away?”) and failure to use headlights during periods of low visibility were oft mentioned but not seriously explored.
Issues that were raised in the US, but given short shrift, gathered considerable momentum in some European countries. Namely, does the visual dominance of DRL equipped vehicles mask or obscure pedestrians and bicyclists? Again, the recent NHTSA study mentioned these possibilities, but did not pursue them. In all fairness this would be a difficult task. Conversely, mandating that millions upon millions of vehicles burn headlights or auxiliary lights during daylight hours is not without considerable cost.
Given the finding of “no statistically significant benefit “in this most recent study it would seem GM could better spend its time petitioning Canada to repeal its DRL mandate.
Read the full study (PDF - 3.2MB)
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46 Responses to “Daytime Running Lights: No Statistically Significant Effect On Safety”
By Dave on Nov 21, 2008
>Does it make a viable case for having lights >on 24/7? NO it absolutely does not!
Thank you for putting that in perspective, Jim.
>Pete:
>But there was a problem at times because of >the fact that when 2 or 3 cars with DRLS >followed by a car without DRLS and then >another car with DRLS it gave the >appearence of a vacant area between them.
Right. That was the fault of the DRLs. It’s like being in a room of polite people, everyone speaking at a moderate conversational level. Some loud, boorish people arrive and thereafter the polite people can’t hear each other.
By Jim on Nov 18, 2008
Pete
That does sound like a low light situation. Does it make a viable case for having lights on 24/7? NO it absolutely does not! It does how ever show that the local police do not enforce a law that is already in effect. Sorry Pete but there is absolutely no reason to have lights on 24/7 I mean, DRLs sorry about that.
By PETE on Nov 18, 2008
We in new jersey recently had four days of rain and misty conditions,and DRLS were a blessing on the local highways. But there was a problem at times because of the fact that when 2 or 3 cars with DRLS were followed by a car without DRLS and then another car with DRLS it gave the appearence of a vacant area between them.If you were approaching from a side road and were trying to get on the highway it appeared that there was no car there and you could proceed safely to on the highway. I cannot believe so much anti- DRLS drivel.
By Jim on Nov 10, 2008
Dave
I couldnt agree with you more!!!
Jeff
I’m still trying to find your point laying around here some where. As for Fleet Admirals comment I would not be opposed to a 5 watt bulb IF and ONLY IF there were regulations against using ANY other type of light during daylight hours witht he exception of bad weather.
By Dave on Nov 10, 2008
Sometimes while driving and getting constantly irritated by DRLs, I feel I’d like to choke the idiots who are responsible. Rather than confront and address the issue of driver competency, they advocated this and apparently without any meaningful regulation. So now you have these typical scenes:
1. Someone driving with 9 gajillion candlepower and talking on a cellphone - WATCH OUT FOR ME; I’M CLUELESS, SO THEY PUT THESE LIGHTS ON ME TO WARN YOU OF MY APPROACH, BY IRRITATING YOU.
2. Driving on the Long Island Expressway at noon on the 4th of July, using my hand to block oncoming cars’ DRLs.
By Jeff on Nov 9, 2008
Fleet Admiral says the Germans really know how to build cars. My old 1984 Chevy Chevette (designed in Germany by Germans)was hardly a high-tech vehicle.
By Jim on Nov 9, 2008
Jeff
Do you have a point laying around here somewhere? I don’t see it anywhere.
By Jeff on Nov 9, 2008
If the Germans really know how to build cars, why did they design the Chevy Chevette as such a low-tech vehicle?
By Fleet Admiral on Nov 9, 2008
And if you’re going to complain about lighting, then you should be focused more on the idiot penny pinchers at the US auto makers who feel it necessary to combine both turn signal and brake light in one housing, making both in red instead of AMBER like they goddamn should be!!
By Fleet Admiral on Nov 8, 2008
If you’ve ever been to Europe, or seen a US spec German car with EURO code headlights that the owner bought from Europe to replace the crap US spec lights, you’d know. Simple, elegant, UNDERSTATED. Audi A4-A6, VW Passat, Mercedes, BMW - angel eyes.
You can also see them on newer ‘03+ US Mercs. They do away with the amber turn signals being on with the headlights - no “parking light” option, and use a 5w “city light” as we like to call them; not DRL. It’s almost the effect of a little christmas tree light being on. Not the pompous 55w garbage US automakers use, and burn out.
By Jim on Oct 31, 2008
Did you just say DRLs look GOOD on a car?? Most car modders take them OFF of thier cars because they take away from the cars apearance. You think they look GOOD? You gotta be outta your mind. BTW those amber lights are NOT mandated in the U.S. mainly because the U.S. does NOT mandate DRLs, period! That is most of the problem in the U.S. aside from the fact that anyone that has any sense at all knows they do NOT improve safety. It’s real simple DRLs have been used for atleast 14 years and you have to do a study to figure out whether they work or not. If they actually worked don’t you think it would be obvious by now?
By Fleet Admiral on Oct 30, 2008
But they just look so goddamn GOOD in my EURO CODE Audi auto-leveling xenon headlight housings. You know, from a country that KNOWS how to build cars and use technology right.
They do headlights PROPERLY, unlike the idiot US carmakers celebrating their 100th anniversary of bankruptcy.
The Audi/VW of old and some current-mainly Euro sold models only, use a 5-thats FIVE watt bulb in the high beam housing as a DRL. Some use 5 LED like the A8, or a hideously implemented row like the A5 which would have been better served with a curved neon type light bar. And the euro code ones do NOT use the stupid parking lights that america mandates. Your drl/headlights are on or off, no amber turn signals to confuse. They only come on when you flip the stalk to turn. Look at an old model 2001-05 VW Passat for this, as somehow they made it past US-DOT at the port. The US code version for older Audi has a holder for the DRL, but did not come with them which pisses us German car enthusiasts off.
As some have mentioned those DRL from chrysler and others are overdone.
If you need to use parking lights, european cars have a feature that leaves ONE side of the cars light on at night depending what side of the road you park.
By Jim on Oct 18, 2008
Sorry folks I been out doing my job all week, 60 plus hours of looking at headlights all day long! Thats not counting going to work 45 min away everyday. Randy you said you needed the lights to see cars “hundreds of yards away”, are you really going to try to tell me you need to see a car 100 yards away? 100 yards is a football field if you dont know and I assuming you would mean atleast 4 or 5 of them, that is a long way off! Dave had a good point and that would be to make DRLs visible only in low light conditions how ever shade in the daytime to me does not quality as low light. Personally I think we need to make drivers responsible for their own lights instead of assuming people are just idiots and doing it for them. If a person can’t resonably know when to turn on lights then why are they driving? Driveing in the U.S. is still a privelage and people should be responsible. Plain and simple DRLs do not work and are just a quick “fix” for a problem no one wants to fix.
By Dave on Oct 14, 2008
I think the only way to properly implement DRLs is to dim them significantly, to a scientifically determined level at which they are not even noticaeble in daylight, except when is quite overcast or the car passes through an unusually shady space.
I you need another car to have DRLs in order to be visible in conditions other than those exceptions, you shouldn’t be allowed to have a driver’s license.
By Todd on Oct 12, 2008
Randy if the road is really dark shaded then I guess yes vehicles should have there parking lights on or DRLS just as long as there is no bad glare. This is more true for dark cars like you said however during the early evening or day DRLS hardly do anything which is probably why it hardly reduces accidents. Like I said before DRLS are ok if they are bright enough without the bad glare but your parking lights are just as good if it is bright enough.
By Jeff on Oct 12, 2008
Australia rescinded the requirement for DRLs on motorcycles after it was found the DRLs did not lower accident rates.
By Randy on Oct 12, 2008
Jim you are not listening. Sure I can see cars around me. No I can not see them a few hundred yards down the road if it is shaded and the cars are dark colored. I am sure you would have a hard time also but you either do not drive those kind of roads or you would not admit it.
Why would insurance companies need to give a discount if it seems like a lot more than 50 percent have them anyway.
By Jim on Oct 12, 2008
Randy, are we taking a trip down sarcastic lane? On the first part of your post, I am at a loss for words to know you need DRLs to see traffic around you. As far as the insurance companies go even if it does cost alot of money with DRLs being as effective as you claim wouldn’t it be worth it?? After all if DRLs are so effective at preventing accidents the insurance companies could save millions per year by giving people inventive to use them. But then again we are being sarcastic aint we?
By Randy on Oct 12, 2008
Ok Jim. I guess DRLs do not work for you. I was glad that cars had them late yesterday and this morning but you were not there. Maybe they did not save me an accident this mornging because I was not passing anyone but it was nice to see that a car was coming. By the way even this time of year the road is often shaded until almost 11 am in the moring by trees and shadows. You have x-ray vision or something that is able to see through such things though.
As for insurance companies not decreasing your premium because you have drls, it costs millions of dollars to set up data processing changes and to implement such a thing. Maybe they do not think it is worth the added cost to implemtent it. I happen to know it is not as easy as flipping a switch to implement those kind of changes. I have worked around dp areas and have seen what things can cost.
By Jim on Oct 11, 2008
Randy, yes, yes, yes 95% of all accidents are avoidable by either driver. It’s a simple fact of life. What were you talking about in your stment about the insurance companies. You do know that insurance companies commonly offer discounts safe driving and accident avoidance stuff right? Three of the top insurance companies DO NOT offer any DRL discount nor do they plan to. Meaning they do NOT see where DRLs save them any money for example, by reducing accidents. Simply put DRLs DO NOT WORK and your just beating a dead horse trying to convince us that a useless safety gimmick actually saves lives. Plain and simple, sorry Randy thats just the facts.
By Todd on Oct 11, 2008
Randy some parts of your argument is right about during the evening vehicles with DRLS is seen more easier and yes at a far distance you can see them better. DRLS have good in some respect but even there effect on safety is very small. During the day DRLS only make a very little difference and during the evening some DRLS have a glare. I guess if DRLS are bright enough without the bad glare it would be fine but putting your parking lights on is just as good. Like I said before if a driver is a good driver then his or she should be able to see anotheir vehicle during the day or early evening without no lights on but the drivers who can’t scares me.
By Randy on Oct 11, 2008
If insurance companies are giving deductions because an auto has DRLs then you could bet it saves accidents and money.
http://www.msnbc.msn.com/id/24111107/
By Randy on Oct 11, 2008
Jim One thing I forgot to mention. Your 95% accident status is wrong. It is not all about paying attention. It is also about judgement. Judgment if you are driving too fast for condtions or other things like passing someone or turning etc. Poor judgment is a major cause of accidents behind not paying attention.
By Randy on Oct 11, 2008
Jim all I can say to you is they work. I do not care about GM. Do you honestly think that the visibility with drls makes no difference? I do not know about all drls on all cars but for the most part there is “no” glare when they use low beams at the 70% or whatever power close to that they are.
If you have a million dollars I would bet you that you can see cars hundreds of yards down the road better than without drls during many lighting conditions. When a car is coming at you at a combined speed of 110 mph to 130 mph or more then the more distance you can see a car the better.
By Jim on Oct 11, 2008
Randy, if a drivers primary concern on the road is driving there would no need for safety gimmicks.I didn’t state it before but I believe you are a victim of GMs gimmicks. Another thing yall don’t realize is GM started this new round of DRL BS because they wanted to save money NOT lives. GM sells in Canada where they do NOT have ample light like we do and DRLs are required. That law is currently being re-evaluated BTW. GM wanted the US government to allow DRLs here so they did not have to use two different lighting systems therefore saving them money! It just so happened that it was GOOD for their ADVERTISING and they could convince people such as yourself that you are profoundly safer behind the when this simply is not true. GM still tells people that DRLs are safety features even though they can’t provide one single shred of proof.
You know if you people really and truely think you have to have DRLs that is ok with me as long as they are AMBER and NO BRIGHTER than marker lights would be. But, this constant glare ESPECIALLY from chrysler cars and GM cars like the monte carlo is just plain reduculous. I guess what Im saying is don’t put a burdon on me because YOU think something other than paying attention and good driving will save your life.
I also posted on this site in another section that 95% of all accidents are avoidable by EITHER driver. All you have to do is PAY ATTENTION. That means leave you cell phone off, try to restrain from your IPod, dont use GPS and most of all PLEASE don’t read a book going down the highway. Yes, I have seen people reading a book at 75 mph!!
One other thing, unless you spend good quality time on the road like, more than say 1500 miles a week I’m not really concerned with how much you think DRLs don’t affect other drivers. Trust me they become VERY annoying very fast and as a result I wear sunglasses most of the time now simply to combat DRL glare.
Oh and Randy I have no doupt that you truely beleive DRLs will save your life after all, that’s what you been “trained” to beleive but, there is NO proof of that what so ever. Apearantly even the insurance companies that are ALWAYS looking for ways to cut cost don’t beleive there is any benefiet to DRLs. How do I know this? I asked three of the top companies one simple question. Do you have a DRL discount and if not, do you plan on offering one? The answer from all three companies……no and no! So even the insurance compampanies don’t beleive the hype.