Re: Headlight use effect on MPG?

The wallet-effect(MPG) on a persons vehicle having DRLs illuminated > is

> exactly what the man posted....virtually nil.

Boy this would be hard one to prove, but I am willing to take a shot at a rough estimate:

Say the DRLs consume 40 watts. Assume the average fuel to DRL conversion efficiency is 25% (and it is not this good). Assume the average person drives 12,000 miles a year and that 65% of this is at times when lights are not otherwise required. Assume the average speed is 35 mph (including highway, town, stop and go). I get the following results -

Total hours of DRL usage = 12000*.65/35 = 223 hours (could be a lot more, or somewhat less)

Energy expended by DRLs = 40*223 = 9 kwh (could be half this or twice this)

Energy consumed to power DRLs = 9 kwh/.25 = 36 kwh = 122,000 BTUs (range is probably 50,000 to 500,000)

1 gallon of gasoline = 114,000 BTUs

Running DRLs for 1 person for one year = 1.1 gallons of gasoline but the range is probably 0.1 to 10 gallons of gasoline. Given today's price of gasoline, that means drivers are probably paying from $0.30 to $30 per year to run DRLs, not including bulb replacement. So, for an individual, DRLs are not all that significant. However, there are over 200,000,000 million cars in the US. If they all had DRLs, that would mean an annual use of over 200,000,000 gallons of gasoline to keep the DRLs illuminated. That would be over a half a billion dollars.

Ed

Reply to
C. E. White
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Its all a scheme by the

wait for it

illuminati.

Dave

Reply to
spamTHISbrp

Ive did the calculations a year or so ago, Ed, and posted them here. My figures were much like yours. The consumption is insignificant, especially when compared with some of the main causes of fuel consumption....high horsepower, large heavy cars, poor aerodynamics.

Reply to
<HLS

I believe the NHTSA has gathered figures in the 450,000,000 to

600,000,000 gallons of gas per year in the US IF DRL's were made mandatory.

Most headlamps are ~55 watts each...so could consume ~110 watts per vehicle (depending on the configuration, if they're dimmed some, etc. would be slightly less)

Reply to
jcr

How could those figures be accurate? You have to take into account the vast number of folks that use their headlights on full power when they drive which turns on all the lights, not just the high beams on half power that most DR's use.

When they don't have to do that, their consumption should drop radically.

Mike

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Reply to
Mike Romain

High-beam DRL's are typically configured to operate at 50% to 60% power (as you mentioned). Headlamp (or low-beam) DRLs are typically configured to operate at 80% power to full power and make up the majority of the configurations out there. (Volvo's and VW's historically have used full power headlamps as DRLs, BTW). Turn signal DRLs are always full power (albeit 23 watts each, so a bit more fuel friendly, but burn out more often).

I don't know what assumptions went into the figures the NHTSA has collected. Although I personally haven't noticed that many people driving with marker and tail lights illuminated during the day (maybe one in twenty at most or less than 5%). Do you see more than one in twenty running with full lights in the daytime? "Vast numbers" seem to imply a large percentage (say over half).

Reply to
jcr

These clowns can calculate this for light usage, yet they don't do anything about traffic lights staggered so that every car on the frigging road spends 50% or more of its time idling?

Reply to
clifto

Well, the open docket is for the study of DRL use. So it would stand to reason that any data collected relating to DRL's use would be part of that. My guess is that general fuel consumption isn't a safety issue (one could argue the added pollution causes health issues, I suppose). In any event, automobile fuel usage falls under the EPA, while auto safety falls under the NHTSA.

Reply to
jcr

For those who feel that DRL's are some sort of personal rights issue then this kind of exercise will provide the justification for unwiring the DRL connection. If fuel usage is really the issue there are many other measures that can be taken that will have enough of an impact in fuel usage that it can actually be measured in daily or weekly mpg averages.

Reply to
John S.

Good point... I dont believe that the mass of the driving public really gives much thought to fuel conservation. If we did, we would plan our trips more carefully, walk or ride bikes more, and buy more fuel efficient rides. We might even carpool.

Reply to
<HLS

But DRLs are also totally unnecessary, so its a huge waste of energy for the whole country.

Reply to
Steve

Coming from a Scandinavian country where they are mandated, I wholeheartedly disagree with you. They can be lifesavers, IMO.

That is not to say that the systems we have here are necessarily well implemented, but the data (which is controversial, Ill admit) indicates they save lives.

Reply to
<HLS

I grew up where fog limited visibility and always use my lights when driving, mandated now or not. I even have a rocker switch on my old Jeep CJ7's headlights so I can just turn them on as daytime lights without my running lights.

I think being seen is important.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

And as is more often than not, I agree with you,Mike'

Reply to
<HLS

GM recently posted to their Chevrolet site under "Safety Features" (and has since changed the page to be less specific with the statistics) that they had documented 423 lives that had been saved in the US over the last 10 years. Given that there are 40,000+ lives lost every year, the number saved (averaging 45 a year) hardly seems as though it would be statistically significant. GM is a huge DRL proponent and that is the best number of lives saved that they can come up with?.

So, assuming $3.00 a gallon for gas, that is a cost of $1.5 billion (give-or-take) a year in extra gas to light DRLs in order to save 45 lives. So is it worth spending $33.3 million to "save" each life? The added deaths from the additional DRL-induced smog may knock off one or two of the 45. ;-)

DRL's are probably not completely useless, but they're darn close to it. And they likely will never pay for themselves on a cost recovery basis I'd bet.

Reply to
jcr

You are too funny!

How do you figure that the 400 or more folks I have avoided hitting because I could see them in the last 10 years, be the only ones 'saved'????

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

if you mean that all those people had lights on and you could see them whereas you couldn't see them if they didn't have their lights on, they should have been manually turning on their headlights anyway. That's just common sense.

Of course, I do realize what I just said there... I just have a knee-jerk aversion to devices intended to save morons from themselves being forced onto *my* car.

nate

Reply to
Nate Nagel

If you need your headlights to be seen, you need your marker lights too.

nate

Reply to
Nate Nagel

A lot of freaking morons will NOT turn on any lights in bad conditions, including rain, fog, twilight, and dawn..

I have done an unofficial survey and at least 1/3 of the people in this "Deliverance" area will NOT turn on lights under severe conditions. It is very dangerous.

We need all the lighting we can get during periods of difficult visibility.

Rednecks tend to shoot the finger at this sort of responsibility.

I have known you a long time, Nate, and know that you are not of this ilk.

Reply to
<HLS

Maybe they're a good idea up near the Arctic Circle where there isn't much ambient light, but for most of the USA there's more than enough light, so DRL's are almost completely a waste of money & gas.

Does anyone here know that GM vehicles, perhaps all vehicles with DRL's, are tested for fuel economy with the Damn Running Lights -disconnected-? How else would GM pass the CAFE bar _and_ have DRLs?

The reason GM has DRLs on US cars isn't because people started wanting them. It's because they are required in Canada, and having common wiring harnesses between Canadian and US cars allows GM to save maybe $5 per car. Notice how the most of the rest of the industry has not made DRL's mandatory. Maybe they are on Volvo's and some others, but at least designers of those cars had the intelligence to let the driver turn them off, permanently.

Reply to
Bob M.

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