Re: Headlight use effect on MPG?

That is correct. Probably 10 years ago GM sought and were granted that testing exception by the EPA. Prior to that, the rule was that any electrical load that was required as part of the normal operation of the vehicle had to exist during EPA mileage testing. (e.g fuel pumps, cooling fans, etc.).

That is indeed the popular version of how DRLs came about. I've never read where GM disputed those "stories" either.

I believe only VW is the only other manufacturer that has made them "mandatory" along with GM. The rest are optional (if you can get them at all).

The last I checked, Volvo's did indeed have a DRL disable switch. I believe nearly all manufacturers have either a disable switch *or* there is a software programming option that the dealer can set for what ever mode the owner wants (DRL or no-DRL). Even GM *could* do it as the disable programming *is* available on newer GM vehicles for government and military customers that request DRLs to be disabled. It is that GM

*won't* do it for "regular" customers by corporate policy for some unknown reason. *AND* the government entity has to sign a release that states that they will re-enable the DRL prior to a change in title. GM getting into the personal preferences of others it seems.

It wasn't my number. It was GM's number (as was explained).

I doubt that you would have had 423 accidents all by yourself these past

10 years had DRL's not existed.

By the way, how does one identify and quantify an event that has not occured anyway?

Whether the buyers wanted them or not has nothing to do with the potential safety features.

There is no intelligence in running without lights in rain,fog, and low light conditions.

You have never lived in a country that uses then. They are a lifesaver and VERY helpful in many different weather conditions.

Second that notion. Totally a waste of energy and downright annoying to have lights on in broad daylight.

They have never been proven to be a lifesaver. It just doesn't happen. There's no way to prove such a thing anyway.

Or the lack thereof.

On Wed, 18 Apr 2007 20:58:03 -0400, jcr rearranged some electrons to form:

Probability and statistics.

As I said, the data is controversial, but it comes from accident report statistics. The studies I know about were done in Denmark.

A few statistics with actual data have to hold at least the same impact as your personal opinion.

Actually I *have* been told repeatedly that I do have some redneck tendencies, but I am not offended at all by that :)

nate

(I mean, is being self-sufficient and able to field-repair machinery anything to be ashamed of?)

You may be right. The NHTSA has been "studying" DRL's for over a decade now and apparently have yet to find enough "proof" one way or the other to rule on the matter (one way or the other). So, we're stuck all the while with dealing with a mixed environment (some cars have them and some cars don't...which is probably even a worse situation!).

I don't DISagree with either of you- but I think DRLs are useless.

The point is that if being seen is a problem, then it is incumbent on drivers TURN ON THE STINKING LIGHTS!!

There's no need on earth to waste energy and annoy oncoming traffic on every bright clear sunny day, which is how DRL's operate 99% of the time. And the OTHER thing DRLs do is make ig'nernt drivers forget to turn the headlights (and the rest of the lights) ON as it begins to get dark. I've NEVER EVER seen so many cars driving without their lights on after dark as I've seen since DRLs started becoming common.

Yeah, northeastern urbanites will be idiots no matter what. I assume that's what you mean, since southern/rural folks are about 100 times smarter than most of the northeastern/urban fools I've met.

Rear-end collisions were one of the accident types documented several years back (by the HLDI in 1997 I believe it was) as having increased rates with DRL-equipped vehicles vs. non-DRL equipped vehicles. This is probably one reason GM now has auto light control sensors on even some of their low-end models so drivers can't drive without tail lights when it's dark...even on purpose. Although, the auto sensors don't often help in daytime fog situations still.

DRLs are also useless when sitting hours-on-end in commuting traffic...when the maximum speed might be spurts of 15-20MPH max between being dead-stopped.

If these knotheads would turn on the lights, then there wouldnt be a problem.

I have been watching them a lot in this state, and on the average only about one in three turns on the lights during heavy rain, twilight conditions, etc (which is mandated by law).

People like this perhaps shouldnt be driving. But the roads are full of them.

Some GM vehicles switch lights on with the wipers as well (but not as many as those that gave the ambient light sensor only). Of course the annoying part of that is your dash digital display devices go dim when ever you use the washer-fluid to clean the windshield. ;-)

While I cannot argue with your equations I have to ask if they take into account over-generation by the vehicles alternator? Do you know if alternators do indeed only put out the minimum required power for any given situation? I would think not as they need to over-generate to recharge the battery. How much excess power is typically generated and how much would that reduce the over-all fuel consumption due to DRL use?

NO excess power is generated. The voltage is held constant at about a volt or so above battery voltage to keep it charged, and this difference is there whether or not any lights are on. If the battery has a resting voltage of about 13 volts, the alternator will put out

14 volts or a little more, and that will be constant regardless of load, until the load beomes so heavy that the field current is maxed out and the alternator can't put out any more. Alternators are sized to the auto's requirements and unless someone has installed huge lights or winches or some other power-greedy machinery, the alternator cannot be maxed out. If there is no load, the regulator will reduce the field current to the absolute minimum needed to produce the battery maintenance current plus the bit needed for PCMs and ignition. You need to study the alternator/regulator functions. They make perfect sense once you know what's up. Even the old electromechanical vibrator-type regulators were able to control the full range of alternator output current, from zero to max.

Dan

"Over-generation?" That makes no sense. The alternator puts out enough current to maintain the bus voltage, no more.

Absolutely. That's the function of the voltage regulator. If the alternator just put out its max power all the time, you'd have 60 volts when driving at 70 mph with no lights or AC on, and 12 volts at idle with the high-beams, wipers, AC, blower fan on max, brake lights, and stereo on.

Nope. The alternator restores the charge of the battery after the engine is started, then throttles back so that it is providing all the power for the electrical loads of the vehicle and nothing more.