Daytime running lights waste gasoline

from "HowStuffWorks.com [by Anonymous Citizen on March 9, 2008]

If daytime running lights were mandatory in the U.S. and all vehicles
had them how much extra gasoline would that use each year?


For several years now Canada has required all new cars sold to have
daytime running lights. Any time the car is running the headlights are
on, but the taillights and other lights are off. You have to turn on
these other lights from the dashboard at night. Studies seem to
indicate that having the headlights on during daylight hours reduces
the number of multiple vehicle accidents (although there has been some
controversy about people forgetting to turn on their other lights at
night -- a mistake that causes extra accidents, and a good example of
the "law of unintended consequences"!).
The US has not adopted this law, but if it did they would definitely
consume gasoline. Headlights require power, and a car's engine
produces power using gasoline. If you make a few assumptions, it is
possible to estimate how much gas the law would consume.

A typical headlight bulb uses about 55 watts; sometimes the daytime
running lights run at a lower wattage so they use a little less power.
Let's say the daytime running lights use 100 watts since there are two
bulbs.

To calculate the energy used, we need to figure out how much time
people will spend with their lights on. According the to NHTSA,
vehicles in the US drove 2,560 billion miles in 1997. We need to make
a guess at the average speed people drive including stops in order to
figure out how much time people spent driving their cars. Let's guess
30 mph, which means each mile takes two minutes. That makes 5,120
billion minutes or 85.3 billion hours. Now if each car normally drives
at night about half the time, that means that the daytime running
lights would be on 42.6 billion hours a year. Multiplying by the 100
watts we get 4,260 billion watt-hours or 4.26 billion kilowatt-hours.
The U.S. uses about that much electricity nationwide in 12 hours.

Now we need to figure out how much electrical energy we can get out of
a gallon of gas. A gallon of gas contains about 60 kilowatt-hours of
chemical energy, but this energy has to go through two conversion
processes before we can use it in a light bulb. First the chemical
energy must be turned into mechanical power by the engine of the car.
Car engines don't do this very efficiently -- only about 25% of the
chemical energy can be turned into mechanical power, and the rest is
wasted as heat. After the engine gets done with our gallon of gas we
have 15 kilowatt-hours left.

Now the alternator on the car has to turn the mechanical power from
the engine into electrical power. The alternator does this a lot
better than the engine, but it is still only about 70% efficient. In
the end we get about 10.5 kilowatt-hours of electrical energy out of a
gallon of gas.

To calculate how many gallons of gas this is, you can divide the 4.26
billion kilowatt hours of energy that the daytime running lights
consume each year by the 10.5 kilowatt-hours of energy each gallon of
gas yields. If daytime running lights were on all the vehicles in the
U.S., we would burn an extra 406 million gallons of gas each year.
That's only a couple gallons for each vehicle, but in total it is more
than all of the vehicles in the country burn in a day. At $1.50 a
gallon, that's $600 million per year. Looking at it another way, an
extra 8 billion pounds of Carbon Dioxide would be added to the
atmosphere by this law.

It's an interesting question because it shows how a simple idea like,
"let's have everyone turn on their headlights all the time" can have a
real cost when you try to implement it! Whether the benefit is worth
the cost is an important question in almost any public policy
decision.

************************************************** **

Now I know some of you will question the date on the article and the
cost of a gallon of gasoline. I did too, but I have no explanation.
I'd love to know where Anonymous Citizen is buying gasoline at a $1.50
per. The rest of the article has some credibility.

On 08/14/08 11:42 am Pete E. Kruzer wrote:

> from "HowStuffWorks.com [by Anonymous Citizen on March 9, 2008]
>
> If daytime running lights were mandatory in the U.S. and all vehicles
> had them how much extra gasoline would that use each year?


<Details snipped>

I bought the DRL module for our US-market 300M and installed it myself.
This vehicle has an "automatic" headlight setting too, so all the lights
switch on when it gets dark enough outside (and when the wipers are on).

The overall cost of DRLs is minuscule compared to the total cost of
running the vehicle.

And remember that the accidents that might have been prevented by DRLs
have a cost too, a cost that may be reflected in our insurance premiums.

Perce

In article
>,
"Pete E. Kruzer" > wrote:

> At $1.50 a
> gallon, that's $600 million per year.

Interesting article, but that gas price is very suspect. <

In article >,
"Percival P. Cassidy" > wrote:

> I bought the DRL module for our US-market 300M and installed it myself.
> This vehicle has an "automatic" headlight setting too, so all the lights
> switch on when it gets dark enough outside (and when the wipers are on).

I Canada the 300M has the DRL function from the factory.
Canadian cars have had DRLs for many years. I find it very helpful even
in the summer on the highway when a car stands out and it's direction is
obvious.

DRL operate in several European countries. In one or two the DRLs are
needed only outside towns.

FWIW.

DAS

To send an e-mail directly replace "spam" with "schmetterling"
---
"Josh S" > wrote in message
...
> In article >,
> "Percival P. Cassidy" > wrote:
>
>> I bought the DRL module for our US-market 300M and installed it myself.
>> This vehicle has an "automatic" headlight setting too, so all the lights
>> switch on when it gets dark enough outside (and when the wipers are on).
>
> I Canada the 300M has the DRL function from the factory.
> Canadian cars have had DRLs for many years. I find it very helpful even
> in the summer on the highway when a car stands out and it's direction is
> obvious.

The theory is interesting. The stated price of fuel tends to date the
original article. Unfortunately, for the sake of argument, I suspect
the stated amount of energy which each gallon of gasoline (what about
diesel?) holds might vary with respect to the particular blending of
fuel chemistries and elements thereof.

A good many years ago, when halogen headlights were starting to become
standard equipment, on the back of one brand's box it touted a benefit
of "additional fuel economy" as a selling point/benefit of using halogen
headlights over then-conventional headlights. Greater light efficiency
with less power input meant the engine had less load from the alternator
to make the headlights work. Another valid theory.

So, if halogen headlights are more energy efficient and allow headlight
manufacturers to state such, then having them run every minute the car
is operating, the whole thing might be "a wash".

IF energy consumption of DRLs was really significant, you could have
expected the environmentalists to have howled when GM made DRLs (and
automatic headlights) standard over a decade ago (in the USA market).
Consumers would be complaining about higher fuel bills, too, I suspect.

In earlier times, some Chrysler products with CA emissions stated to
have the low beams turned on when you set the base idle speed of the
motor. In these situations, the additional load of the headlights (back
then) might change the idle speed slightly, which would then need to be
compensated for in the idle speed screw adjustment. Usually, this was
on Slant 6s rather than the V-8s. I suspect that as soon as the motors
came "off idle", the issue of alternator loading went away as the carb's
main system metering calibrations took over.

This could well be another situation where, individually, the energy
consumption might be measureable in the lab and insignificant in the
real world, but when collectively considered, becomes significant. Just
like changing an air filter or keeping the tires fully inflated "to
specs" can have similar or more significant effects on a vehicle's mpg.

Regards,

C-BODY

wrote:

> IF energy consumption of DRLs was really significant, you could have
> expected the environmentalists to have howled when GM made DRLs (and
> automatic headlights) standard over a decade ago (in the USA market).
> Consumers would be complaining about higher fuel bills, too, I suspect.


Most environmentalists don't know how to decide whether to howl or not.
They need an Al Gore to tell them what to howl about.

Its simple to calculate how much energy DRLs take. About 50 watts of
electrical power, or roughly 1/16th of a horsepower. Not particularly
insignificant, since a modern aerodynamic car only needs a few
horsepower total to cruise at highway speed. Multiply by the millions of
cars on the road....

On 08/26/08 11:33 am Steve wrote:

>> IF energy consumption of DRLs was really significant, you could have
>> expected the environmentalists to have howled when GM made DRLs (and
>> automatic headlights) standard over a decade ago (in the USA market).
>> Consumers would be complaining about higher fuel bills, too, I suspect.

> Most environmentalists don't know how to decide whether to howl or not.
> They need an Al Gore to tell them what to howl about.
>
> Its simple to calculate how much energy DRLs take. About 50 watts of
> electrical power, or roughly 1/16th of a horsepower. Not particularly
> insignificant, since a modern aerodynamic car only needs a few
> horsepower total to cruise at highway speed. Multiply by the millions of
> cars on the road....

But, as I wrote upthread:
.... remember that the accidents that might have been prevented by DRLs
have a cost too, a cost that may be reflected in our insurance premiums.

And not just our auto insurance premiums, but our health insurance
premiums too. And the taxes that go to law enforcement to investigate
those accidents* and to fire/ambulance/rescue services to rescue people
from those accidents.

*I still don't understand why the police are supposed to be called to
every little fender bender that involves only a few thousand dollars of
property damage and no bodily injuries.

Perce

Percival P. Cassidy wrote:

> But, as I wrote upthread:
> ... remember that the accidents that might have been prevented by DRLs
> have a cost too, a cost that may be reflected in our insurance premiums.


Call me a skeptic, but I don't think they do ANYTHING to prevent
accidents. Sure, when they were new and conspicuous, they might have.
Now, half the cars on the road have them and they don't draw any
attention at all. If you need lights to be seen, its time to turn on the
headlamps. No reason to burn energy needlessly on a bright clear sunny day.

In article >,
Steve > wrote:

> Call me a skeptic, but I don't think they do ANYTHING to prevent
> accidents. Sure, when they were new and conspicuous, they might have.
> Now, half the cars on the road have them and they don't draw any
> attention at all. If you need lights to be seen, its time to turn on the
> headlamps. No reason to burn energy needlessly on a bright clear sunny day.

We've had them for almost 20 yrs in CDA and believe me they help.
On the highway you can tell from a distance that a car is moving, even
on a bright sunny day, particularly if you are going towards the sun.
Also much better than the full head lights when conditions are bad, such
as in a rain storm, or none because people forget to turn them on.

I would like to see a change or ban on those too white, too bright,
blinding discharge headlights.