Jalopnik
When we were kids, we loved that "Way Things Work" book. Although we absorbed very little from it, it was always fun looking at the pretty pictures and diagrams. HowStuffWorks.com is the net equivalent of that book, and just like the book, we absorbed very little from the text. Take for example the question posed by the following article on the site:
If daytime running lights were mandatory in the U.S., and all vehicles had them, how much extra gasoline would that use each year?
Except for a couple of major points, the majority of it went in one ear and then out our anus — everything that is, except the following salient details:
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.
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.
Whoa — that's a hella lot of extra gas. So although it's only a couple of extra gallons per car, in total it ends up being more gallons of gas than all of the vehicles in the USA burn in a single day. That is a hella lot of gas. Damn you safety experts! That's it, tonight when we're driving home from the bar, we're turning our headlights off in protest — we're gonna save us some gas come hell, high water or massive internal injuries resulting from head-on collision. [Hat tip Zerin!]
If daytime running lights were mandatory in the U.S., and all vehicles had them, how much extra gasoline would that use each year? [How Stuff Works]
Comments
30mph? Seems a bit low for an average.
Ok, that's assuming there's additional load on the alternator required to power the DRLs. I don't believe that's the case; I think a healthy alternator is producing *more* electricity than is used by electric system of the car. So using your DRLs or turning on your headlights or crankin' the Husker Dü up to 11 is just using excess juice that would otherwise be turned into heat.
What's next? We all turn down our stereos by three notches and save even more gas? Followed by the A/C off below 75 degrees campaign... followed up by... you get the point. It'd be different if the calculation was correct, but I agree with balor. There is virtually no savings. I'd be curious to know how many accidents have been avoided because of day time running lights. Imagine how much gas is saved by not having those accidents, destroyed cars etc (not to mention burials... hearses get AWFUL gas mileage I tell you). Calculate that! HA.
If anyone actually wanted an easy way to save a substantial amount of gas, we'd drive the speed limit. I know I sure don't.
Well, I know that if you don't put a load on an electric generator (alternator, whatever) it has significantly lower resistance than if there is a load. If the battery is fully charged, I would imagine this lack of a load on the generator would cause it to spin much more easily. Isn't this the logic behind turning off the A/C?
No, Adam, the logic behind turning off the A/C is that when the A/C is running, the clutch on the A/C compressor is engaged, turning said compressor with engine power via the belt drive system. This compressor requires a significant amount of power to do its job (The number 5 HP jumps to mind, but I'm not sure if it is correct.) The fan that pushes the air itself uses slightly more juice than the headlights, and is subject to the argument above. Does anybody here know for sure how much HP an A/C compressor requires to do its job?
Headlight fluid is much cheaper than gas.
Adam...
My Viggen showed an average of about 25 MPH over three years of typical commuting. And I dont drive slow...
blalor...
Last I heard energy is never free, output can't be more than input and alternators don't store energy.
the alternator has 2 major functions
-keep the battery charged
-generate power to the spark plugs
once the battery is charged that power gets turned into heat. the torque load on an alternator doesn't change regardless of the electrical draw on the car. Therefore if you're not powering something while you're driving the extra energy is wasted.
With an a/c compressor the torque load does change when it's activated, so it draws more power from the engine.
This article basically debunked itself. How many times can you say "lets assume" before there are just no solid facts from which to form an hypothesis?
Still though, I'd like to see mythbusters do a segment like the "tailgate up or down" myth only do headlights on or off... where they drive out an entire tank of gas in 2 identical trucks and see if one runs out first.
I have disabled the DRL on each and every car I have that came with them; I find (as a motorcycle rider) they de-sensitize people to headlights, which is the ONLY thing that keeps motorcyclists alive sometimes, AND they have glare, AND they are completely useless in broad daylight in the lower latitudes.
If I wanted my headlights on, I would switch them on. I am sickened by the creep of Big Nannyism from our Gubment and industry.
Let's not forget the gas saving tip of proper tire inflation and rotation.
Speed limit reduction only makes a big difference if your car isn't geared for higher speed highway driving.
Watch the tach. The lower it is, the less gas you're using.
People drive their cars 50% during the day and 50% during the night? Where? Above the arctic circle?
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