The mpg confusion
What reduces emissions more?
A. Someone swapping their old SUV (which gets 12 miles per gallon) for a hybrid version (18 mpg) or
B. someone upgrading their 25 mpg compact to a new 46 mpg Prius?
(ignore for a minute manufacturing issues or driving habits and assume the miles driven are the same).
The surprising answer (for those who don't work it out) is A. It's easy enough to see why this is the case. If the driving distance is 100 miles, then for case A the saving in fuel used (and hence emissions) is 100/12-100/18 = 2.8 gallons, while for B, you have 100/25-100/46 = 1.8 gallons. The confusion arises because people like to think linearly about numbers, not inversely, and so tend to assume that a similar change in mpg has a similar impact on fuel usage. This is not however the case - improvements in efficiency at the low end of the scale are much more useful at reducing emissions. This is actually a very general point - when trying to raise efficiency it is always sensible to start with the least efficient processes.
This confusion got some attention a couple of months ago after a piece that was published in Science by Larrick and Soll. They tested peoples instinctive reactions to changes in mpg numbers and found that people very often got it wrong, leading to less than optimal decisions. They also tested a different way of giving fuel usage information (the number of gallons used per mile), and since this is linear in emissions, people made the correct judgment much more often (it's worth noting that the standard in most of Europe is already litres per 100 km). Rewritten in those terms, the choices above become:
A. Someone swapping their old SUV (which takes 8.3 gallons to go 100 miles) for a hybrid version (5.6 gallons/100 miles) or
B. someone upgrading their 4 gallons/100 miles compact to a new 2.2 gallons/100 mile Prius?
Much easier, right? The authors of the Science piece are trying hard to get US manufacturers and the EPA to switch over from mpg to this new standard (though they prefer gallons/10,000 miles). It all seems eminently sensible to us.
23 September 2008 at 11:30 AM
Here’s what I think is eminently sensible: my 1991 Ford Festiva which gets 38 MPG in stop-and-go city driving and 48 MPG on the highway (approaching 2 gallons/100 miles), using the technology that was available 18 years ago.
23 September 2008 at 11:41 AM
I note that mileage is quoted in Canada (and I think elsewhere in the world) in liters per 100 km, which makes this much clearer.
How about the person who gets rid of their old SUV and buys a hybrid compact?
23 September 2008 at 11:51 AM
Of course someone switching from his old (8.3 gallon fir 1oo miles) to either a compact (4 gallons for 1000 miles) or a Prius (2.2 gallons for 100 miles) will do even better. Or, suppose the auto manufacturers produced larger vehicles for those who need the space which could get go 100 miles on 3 gallons.
In passing, I saw Frank Lutz on The Colbert Report, who was explaining why GM was producing the Volt when he still doesn’t believe in global warming. Lutz came up with the old story about the 30,000 scientists who agreed with him that human activity wasn’t the cause of the warming. Colbert didn’t challenge him on that, which I think was a shame, but he did ask him just whom he expected to buy this new car if global warming was a myth.
23 September 2008 at 11:52 AM
People have a hard time comparing inverses, so gallons/10,000 miles is a step in the right direction. But 400 gallons/10,000 miles remains an abstract concept.
4 gallons/100 miles is a concrete concept. It means something immediate.
I do not see what the attraction is of gallons/10,000 miles. Is it just a gratuitous rejection of the (familiar to some) litres/100km measure?
I wanted to use the word “reci…cals” instead of “inverses”, but hte spam filter saw a bad word imbedded in it.
23 September 2008 at 12:00 PM
The argument loses some of its weight if we have to ignore manufacturing issues (i.e. the CO2 generated in the manufacture of a new car).
Going a little off topic… it’s a bit like the solar energy discussions where the the CO2 generated in the manufacture is almost always completely ignored (along with the extra costs associated with regular cleaning required for both solar panels and mirrors)
[Response: All analyses need to use the full lifecycle in order to be useful for decision making. However, this point is simpler than that. - gavin]
23 September 2008 at 12:13 PM
Yes yes, but the absolute amount of fuel required to travel those 100 “miles” still makes for a good anti-SUV argument. So what’s the point of showing that efficiency gains are more for a small improvement in a very inefficient system, rather than for a larger improvement in a very efficient system? Michaelis Menten graphs, saturation curves etc.
23 September 2008 at 12:22 PM
How to account for things like PZEV, SULEV, ULEV? Are the emissions from a 15 mpg engine actually double those from a 30 mpg engine? What about the age of the engine? What about gas vs. “clean diesel” vs ethanol blends? I’ve even known someone who ran his pickup on propane, and I have NO idea what the emissions from that are like. What about oxygenating the fuel? What about someone who replaces part of his driving with riding a motorcycle or scooter? What about a vehicle (like the upcoming Volt) that gets some of its power from plugging into the grid? How do you calculate the impact of that?
I know, I digress somewhat, but as fuel choices get more diverse, the general public probably gets more confused …
[Response: Emissions are very closely tied to the fuel usage. Different fuels have different emissions per gallon (depending on the molecular structure - i.e. how many carbons, denisty etc.), so you need to be careful comparing mpg from a diesel than from a petrol engine. Hopefully someone knows a good source on this? As for ethanol blends, it all comes down to where the ethanol comes from. If it’s from corn in the US, emissions are basically the same as if it was pure gasoline (due to the fossil fuel use during production), if it’s from sugarcane in Brazil, net emissions are significantly lower. Plug-in hybrids benefit from the more efficient use of fossil fuels in electricity generation even now and so have lower emissions than internal combustion engine cars, and if they get their juice from renewables, emissions would be very low indeed. - gavin]
23 September 2008 at 12:38 PM
What an excellent idea. Totally fresh view for evaluating mileage. Thanks for getting us thinking in that way.
Of course total energy costs to manufacture that Prius should be considered. So I will keep my old Isuzu Pooper - and just drive it fewer miles. Because that saves all the energy that goes into a new car manufacturing.
The next measurement consumers need is to know how much energy goes into products and services. Take for instance a cup of coffee. Measure the growing, picking, shipping, roasting, grinding, brewing, containers etc - all are energy intensive. I am sure that Starbucks knows precisely how much energy goes into a typical cup of coffee. I bet it is surprisingly high.
All products need to show a rating of this energy - we might make a Starbuck the moniker for a standardized energy measurement.
So any item could be rated by the starbuck standard… or without a brand name - just to think of how many coffee-cup-energy-units are in any item.
Think of how much better decisions we could make.
23 September 2008 at 12:57 PM
Good post. In a related matter, the exclusion of vehicles “expected” to be used for business from CAFE (Light trucks - all before, now over 8,500 lbs GVWR) is bad policy for the reasons you gave as well as because business vehicles travel far further! Thus, the argument for excluding business-type vehicles from CAFE is backwards. They should have been regulated first. Consider taxis, for example. They should all get absolutely the best mileage possible.
Ethan, perhaps everyone should get a set amount of gas at normal prices, and as much over that as desired with a $10 a gallon tax tacked on. That might get a few folks to downsize. Too bad it would take record-keeping or ration cards or whatnot. Then again, the planet just *might* be worth the inconvenience… Captcha agrees: to permitting
23 September 2008 at 1:54 PM
I think liters per 100 kilometers would be better than gallons per 100 miles (why 10,000 miles?). We from europe have a few problems with miles and gallons
23 September 2008 at 1:57 PM
Please be advised that we in Quebec and the rest of Canada already use liters/100km. So it’s not only in Europe!
Richard H.
23 September 2008 at 2:13 PM
The person switching to the Prius is going to be saving a factor of 1.84 on fuel while the other switch only saves a factor of 1.5. If fuel cost is what is bothering you, you are probably already driving the compact and you have more motivation. If we really want to tackle bulk fuel use, we should go to rationing. This works better than price signals when the ability to pay is so broadly spread. It can also make an energy trasition much much less costly: http://mdsolar.blogspot.com/2008/06/oil-is-too-expensive.html
23 September 2008 at 2:14 PM
What’s always puzzled me is the “need” for a huge great big car. “So we can drive in comfort with the kids when we go on holiday”.
So rent a big car.
Especially in the US when there are so few holidays, they are spent like gold dust, they aren’t going to be highly contested on any one week.
Rent it.
Borrow it.
And have a car appropriate for the normal use. With the *possibility* of sub-optimal use of the smaller car for transporting all the kids.
23 September 2008 at 2:17 PM
rpauli, #8.
Do you know what the most recycled (and most efficiently recyclable) part of a normal car is?
The batteries.
The prius batteries WILL be re-used.
Heck, the reason why electric cars as expensive is because the batteries are expensive. WHO THE HELL is going to throw THAT away???
Especially when you know that a big current theft is taking the copper lines used for telecoms and selling the copper. DIGGING UP THE COPPER IS WORTH IT!!!
23 September 2008 at 2:28 PM
Richard, I didn’t say that. I suppose that there are a lot of countries besides Canada and the EU which use litres per 100 km. As far as I know only the USA uses mpg. From my point of view a change from mpg to gallons per 10,000 miles is only a small step in the right direction (I had to look up the conversion for gallon in litre and mile in km).
23 September 2008 at 2:31 PM
Perhaps it is easier to measure the emission of CO2 produced in grams of CO2 per distance. The European Union had a voluntary agreement to reach an average of 120 g/km for all new passenger cars by 2012.
23 September 2008 at 2:45 PM
RE #13 Mark:
I’m with you, man. We got rid of all our cars and cycle everywhere now. Just strap a kid to each thigh, one across the pannier racks and another on my back and we’re away (I only make the wife carry one kid).
Of course, visiting the relatives on the weekend can be a bit of a chore. By the time we’ve ridden the 135 miles there, it’s almost time to turn around and go home again. But it’s worth it for the warm inner glow I get from knowing our family’s carbon footprint is almost negligible.
23 September 2008 at 3:10 PM
Well, there is a better choice - but let’s take the lifecycle approach:
1. Set up a solar PV manufacturing factory that derives all of its power from solar panels.
2. You will also need a polysilicon plant to feed high-quality silicon wafers into the solar PV plant, such as this one:
http://www.reuters.com/article/pressRelease/idUS182891+15-Feb-2008+PRN20080215
3. Now, we have ourselves a solar breeder facility. In goes silica ore, out comes finished PV panels, and no fossil fuels are involved in the PV manufacturing process.
4. Take those solar panels and set them on top of carparks or home garages, or feed the electricity directly into the grid.
5. Build an electric car manufacturing factory, and surround it with enough solar panels to power the manufacturing process.
6. Take your electric car, charge it up with your solar panels, and you have a fossil fuel-free transportation system.
Zero emission transportation. All the elements already exist - they just have to be put together.
Now, we can port this concept to agriculture systems, which are heavily dependent on fossil fuels - solar / wind powered water pumps, electric farm equipment, even fertilizer.
Currently, fertilizer is made using natural gas (steam reforming of methane to generate hydrogen to feed into the Haber process) - but with the new advances ( http://www.greencarcongress.com/2008/07/researchers-at.html ), it should be possible to generate that hydrogen directly from water using sunlight; feed the hydrogen into the Haber process (energy expensive, true, but doable), and then you have your ammonia, convert half of that to nitrate, and there you have your ammonium nitrate fertilizer, which currently accounts for about 1/2 of all agricultral fossil fuel use.
So, now you have your fossil fuel free agricultural system, zero net emissions, with equivalent productivity. Whatever you grow that you don’t use for food can then be fed into biofuel production (as well as biochar production, as a soil amendment, meaning NEGATIVE emissions), and then you have some amount of ethanol, biodiesel, or bio-based hydrocarbon product. This lead us to:
7. Take your hybrid Prius, fill it up with that zero-emission biofuel, and you have the equivalent of a solar-powered electric car, emission-wise.
So, those are two routes to zero-sum-emission transportation, as well as route to zero-sum-emission agriculture.
Here’s a good question, though: how do you transport container-loads of raw materials all around the world without access to cheap fossil fuels? By sail?
Well, ideally you don’t do that at all. Instead, you only ship high-value goods (laptops, refined chemicals, solar panels) and you eliminate the global trade in raw materials - because it is just too expensive.
Those are the kinds of approaches that will be needed to get past the Fossil Fuel Age, which will end due to replacement by superior technology, which is also how the Stone Age ended.
I bet the makers of stone tools were just as upset about their loss of market share to the bronze tools as our fossil fuel CEOs and investors are about their own eventual downfall. Did they also carry out massive PR campaigns in the hopes of holding off the inevitable?
23 September 2008 at 3:10 PM
Interesting post. I passed it on to my SUV-loving family members…
Gavin, I realize that the life-cycle analysis was not the point of this post, but I think it would be a great future post. Do you have access to some good articles on this topic?
Does the life cycle analysis of a prius vs a hummer actually give the hummer a smaller carbon footprint? (I doubt this, but I’ve seen an article suggesting that it is true). I know I know, not exactly climate science…
23 September 2008 at 3:13 PM
So Mugwump…
Did you miss the rest of Mark’s post on renting or borrowing a vehicle when you need more capacity or is your sarcasm of the lightweight variety???
23 September 2008 at 3:31 PM
Another confounding factor is that, except for inexpensive staples, people use less when a product becomes more expensive, and use more when the product is cheap. Essentially, people spend more money when they make more money.
So I suspect the answer isn’t as clear cut as it was stated in the blog post. The answer if a study were done might amaze Gavin. That is, it might not be ‘A’.
If the driving distance is 100 miles for a person in a 12mph SUV, then the driving distance might drastically increase to 130 miles for a person in a 18mph SUV. If the driving distance is 100 miles for a person in a 25mph car, then the driving distance might only become 110 miles for a person in a 46mph hybrid.
Then for case A the saving in fuel used is 100/12-130/18 = 1.1 gallons, while for B, you have 100/25-110/46 = 1.6 gallons.
The confusion arises because people like to think statically about demand, not dynamically, and so tend to assume that a set relationship between change in effective supply (mpg) has identical (or no) impact on change in demand (car usage). This is not however the case - huge drops in cost for a staple that uses a perceived significant portion of income drive up usage more than they do for a huge drop in cost for a relatively cheap staple.
23 September 2008 at 3:33 PM
This analysis reminds me of relative risk versus absolute risk in risk assessment. Your analysis is certainly correct but the relative change in gas mileage for the SUV example is 33.7% (2.8/8.3) compared to 45.0% (1.8/4) for the Prius example. In relative terms, the compact-to-Prius change is greater. Did I get that right? There are many different ways to think about this, but the instincts of linear thinkers are correct in terms of environmental outcomes: assuming equivalent CO2 etc. output per gallon of gas burned, the final outcome of the SUV change is two and a half times more damaging to the environment than the outcome for Prius change.
[Response: I disagree. The issue is the total amount of emissions, not how important the relative improvement is. - gavin]
23 September 2008 at 3:40 PM
I think that this is a good transition to make. The framing of the energy consumption will help consumers make more effective decisions on their fuel use.
The decision of whether to switch should be separate from when to switch vehicles. If a vehicle is replaced at the end of its service life (or near it), then the issue of energy cost in its manufacture are less important. I would guess that energy costs of production of vehicles is related to the mass of the vehicle.
I think this concept could be stretched to show the fuel consumption per 100 miles at various speeds. Over the past two weeks, I tried driving on the freeway at 60 mph instead of 65 mph. Traffic conditions allow this easily. I travel 45 miles each way on the freeway, and my fuel consumption in mpg went from 50 to 55.
(or 2 gallons / 100 miles to 1.8 gallons per hundred miles). The cost in time: about 5 minutes. (I drive a Prius, in case anyone is wondering.)
In addition, it would be useful to know the energy cost (or relative energy cost) of more consumer items. The EnergyStar program has some severe problems, but it is a start. Energy consumption of other items is usually ignored (computers, for example).
Finally, I think we need some concept of a level of energy consumption, or carbon footprint (take your measurement) that is acceptable with reference to preventing AGW.
Measuring carbon footprint is complex - if you have not tried to do this, try it. It is complicated. How do you account for the aspirations and goals of folks - often related to a standard of living measured by wealth?
One example: if I believe that AGW is real (I do) and I should minimize my carbon footprint (I try) how much air travel can I justify for pleasure and / or business?
[Response: One of things I’ve noticed with drivers of hybrids is how their driving habits change if they have the mpg numbers on a real time display on the dashboard. That is, they drive to keep the numbers up (like a video game). I’m pretty certain that increasing the use of such displays in all cars would improve overall efficiency without any change in the fleet. - gavin]
[…though it might also increase accidents. I find I’m often looking at the darn screen instead of the road in my Prius…–eric
23 September 2008 at 3:49 PM
Efficient driving is secure, easy and fun!
A New Fuel Saving Device Can Change the Way We Use Fuel Driving Our Car.
Using the momentum of your car will reduce your fuel consumption; The U.S. Patent Office issued a Patent for Moment-O-Meter.
When Tom presented me his work, I was skeptical because it was utterly simple and logical, thus not new. It took thousands of years to put wheels on our luggage because nobody thought about it.
Clearwater, Fla. (PRWEB) August 20, 2008 — GREEN TECHNOLOGY MFG manufactures the long awaited Moment-O-Meter, a consumer friendly device that helps to reduce fuel consumption (patent # 7,411,140).
“It may take ten years for car manufacturers to create and redesign higher fuel efficient cars, fifteen years to find and exploit fuel fossil reserves in the US and maybe twenty more years to develop safe nuclear energy providing 50% of our electricity,” said the inventor, Tom Delor.
It takes only a few seconds to stick Moment-O-Meter to your windshield and plug it in your cigarette lighter to upgrade your car to a fuel efficient car. “Moment-O-Meter was developed and tested during the last three years, and we now manufacture it in Clearwater, Florida,” added Delor, a retired ex-aeronautical engineer who co-invented this device to help his school teacher daughter to save gas. “It all started with my daughter and I’m always looking for a good reason to spend some time in my workshop,” added Delor.
As Speed-O-Meter indicates the speed of a vehicle, Moment-O-Meter indicates its inherent momentum allowing users to coast by, moving their car effortlessly by force of the inertial mass generated. Green light indicates you can coast, red light indicates you need to use fuel to maintain the car’s speed. It’s like a personal trainer telling you what to do.
“Every driver can take advantage of their car’s momentum to drastically increase their fuel efficiency if they are shown how,” the inventor said. “You will save 20% to 50% gas the very first time you use it. To make it work for everyone, it had to be simple and visual. Moment-O-Meter is very simple; just react to the device’s lights to save gas. I personally save 50% but my wife saves only 32% … It still depends on the driver’s skills, but improvement is expected as driving efficiently will become second nature,” concluded Delor.
About GREEN TECHNOLOGY MFG
GREEN TECHNOLOGY MFG, located in Clearwater, Florida, is the developer and manufacturer of this long awaited new instrument for cars. The device uses simple visual cues to allow drivers to take advantage of the moving vehicle’s momentum. It really does not matter if the vehicle uses gas, ethanol, or electricity or if the vehicle is a small or an eighteen wheelers. Retired ex-aeronautical engineer Tom Delor is the co-inventor, and patent attorney John Rizvy from Fort Lauderdale, Florida said: “When Tom presented me his work, I was skeptical because it was utterly simple and logical, thus not new. It took thousands of years to put wheels on our luggage because nobody thought about it.” Comparatively, nobody thought about showing the momentum of a moving vehicle until now, replied Delor. With the energy crisis, necessity became the mother of all inventions and the United States Patent Office by issuing the patent confirmed that Moment-O-Meter is a genuine new invention.
More information:
http://www.extra-mpg.com
23 September 2008 at 4:18 PM
http://priuschat.com/forums/prius-hybrid-news/30974-prius-vs-hummer-exploding-myth.html
RE: Number 19 - Hummer vs Prius. the linked post discusses this illusion that is floated about on the web
23 September 2008 at 4:35 PM
Instead of changing the car, why don’t we change the town. High density housing in the city, then farms and parkland. No suburbs.
Would that fit the American dream?
23 September 2008 at 4:39 PM
I agree that it’s easier for me and others to compare cars in gallons/hundred miles.
Re the GHG cost of manufacturing, there may be a newer analysis, but I use this one: On the Road in 2020 (pdf)
Re the cost of flying, there are lots of assumptions around because of different ways of using or ignoring a 1999 report on aviation’s role in global warming [Aviation and the Global Atmosphere] for the Intergovernmental Panel on Climate Change—the effects of flying are much worse than would be predicted by just burning the oil.
Atmosfair calculates GHG emissions for flying, multiplying the effects of time at high altitude by 2 (IPCC said 2 - 4) and incorporating information about whether the flight was nonstop.
Life cycle cost of a hummer is a great deal more than for a Prius.
23 September 2008 at 5:00 PM
The embodied energy requirement (not just fuel economy) for replacing the entire fleet will be crucial when things get tougher. As others point out it may be difficult to produce enough metal and glass in a solar economy to even make cars let alone finding energy for propulsion. So far as I’m aware no-one has done a life cycle analysis of the Pickens plan as it affects cars. Under one scenario existing SUVs could get a $2000 conversion to compressed natural gas. Drive those cars for another 10-20 years and that saves a whole lot on replacing them with Priuses with an embodied energy equivalent to say 900 USgall or 3400L of fuel. I’ll omit the calculations.
23 September 2008 at 5:04 PM
#3: I could very well be an anthropogenic global warming skeptic and buy a GM Volt. I think driving a noiseless e-car and possibly saving on traditional fuel could be a strong incentive, with no need to push it up with climate considerations. BTW New Scientist (20 Sep.2008) has an interesting comparison showing that plug-in hybrid electrical vehicles (PHEV) will emit about the same 95 g CO2eq/km regardless if the electric power comes from nuclear or renewabels. Greenpeace and others are trying to impose a still stricter 80g/100km maximum here in Europe, what makes me wonder if these enviros will ever be happy with an achievement, or continue to ask for the impossible , regardless of the difficult job of the scientists and engineers who made the first reduction happen.
23 September 2008 at 5:06 PM
Oxnardprof wrote about the improved mileage at lower highway speeds. He notes that it took only 5 minutes longer on his 45 mile commute. Recently, I wondered how much one would “earn” as an hourly wage in terms of the money saved per hour of extra travel time due to the lower speed. For some typical cars I looked up the mpg vs speed graphs, and assumed $4/gal gas. In the end I was kind of disappointed because the hourly “wage” was only $8-9 for a 20 mpg car and less for a 40 mpg vehicle, something like minimum wage. So you save more per hour with the gas guzzler, a fact that is closely - but not obviously - tied to the original question in this post. I was hoping for a higher hourly wage because it could be a strong incentive for people to slow down. In the end I decided that a better way to present the message is to cast it in terms of dollars saved per 100 miles…or maybe in terms of a reduced effective cost of a gallon of gas. People are very sensitive to the latter.
23 September 2008 at 5:27 PM
If hybrid (or eventually all alternative fuel) cars and hybrid commercial airplanes (imagine that!) were made more affordable than the traditional vehicles, I would imagine more people would take that route regardless of how much they understand or care about global climate change.
23 September 2008 at 5:28 PM
#27, the link “On the Road in 2020″ is broken.
23 September 2008 at 5:41 PM
Miles per gallon: ug! Gallons per hundred miles: a bit less bad. Litres per hundred kilometres: better still. Kilograms per hundred kilometres, best.
kg/100 km is an improvement because the volume of a given mass of petrol changes (very slightly) with temperature and it’s the mass (not volume) burnt which determines both the energy available and the emissions produced.
Airliners (747-400s, I believe) flying Hong Kong/London have their fuel chilled before loading to be able to get a larger mass into the fixed volumes of the tanks.
The UK still mostly uses miles per gallon but l/100 km is used a bit.
23 September 2008 at 5:46 PM
Larry, #30.
That would only be lost OPPORTUNITY cost.
How much would he earn if he didn’t go for a number one and wore incontinence pants?
How often would he lose 5 minutes from a productive work day? Would he lose *any* pay over it?
If he’s salaried, he’d earn exactly nil.
If he’s on hourly, he has to spend 10 minutes at work. IF anyone is minuting him that closely. Which they aren’t.
23 September 2008 at 6:04 PM
At the risk of swamping people with numbers, I’d like to see no less than three numbers quoted:
miles/gallon, cost/mile, g CO2/mile.
energy density, cost efficiency, and carbon intensity are three separate topics, yet all are relevant to the driver.
This becomes more important as we begin to see a variety of fuels and blends available.
23 September 2008 at 6:34 PM
But, when upgrading to a more fuel efficient car, you tend to sell your old car to someone else. So the effect is actually additive. There are now two cars on the road rather than one, irrespective of whether one is more fuel efficient than the other.
So really we should be crushing and recycling our old cars, rather than trying to recoup some financial return by selling them on and feeling smug about our new hybrids. :^)
23 September 2008 at 7:04 PM
On the Road in 2020: http://lfee.mit.edu/public/el00-003.pdf
Re the Pickens plan, I heard Lee Schipper talk a couple of weeks ago. Compressed natural gas does 10% better than gasoline re GHG emissions, except that the natural gas will come from Indonesia and there will be a lot of leakage if there are a lot of vehicles. Such was reported in a recent bus/train collision in LA.
23 September 2008 at 7:17 PM
Another benefit of reducing driving speed, if all drivers reduced speed, is a reduction in traffic congestion. This was discussed in the NY Times not long ago, but if there is an incident blocking traffic, and highway speeds are reduced, then fewer cars will get caught in the delay, and traffic jams are reduced. Thus reduced highway speeds in urban areas would reduce fuel consumption both by reducing gallons per mile consumed when traffic is flowing, and by reducing the duration and intenstiy of congestion when traffic is blocked.
23 September 2008 at 7:20 PM
Gavin #7
“so you need to be careful comparing mpg from a diesel than from a petrol engine. Hopefully someone knows a good source on this?”
Maybe this can help: http://www.epa.gov/oms/climate/420f05001.htm
Gasoleum is a heavier oil and therefore has a higher carbon density per litre than gasoline. However, on average a diesel engine tends to be between 30% to 40% more eficient in fuel consumption than its equivelant engine size petrol counterpart, therefore, per km the diesel engine will emit less.
The caveat here are the new hybrid gasoline engines which dramatically improve petrol fuel consumption, which coupled with the lower carbon density of the fuel make them lower emitters than an equivelant engine size diesel.
I imagine that if a viable hybrid diesel engine is developed this will outperform the current toyotas and hondas by an equivelant margin of the other conventional engines.
23 September 2008 at 7:35 PM
I do my best thinking while walking, so I walk to the market almost every day. I like to bicycle for exercise, so many of my “round about town” chores are done on my bicycle. If I have to be at the EPA in SF at 9:00 in the morning, bike/BART is far and away faster considering traffic and parking. My bike will get me to BART, and BART will get me to both airports, so “round about town” includes day trips by plane. (in nice weather)
My point is the real measure of transportation efficiency is pounds of carbon per task, and for that, even the Prius comes out way down the list.
23 September 2008 at 8:11 PM
China and the U.S. have a similar level of net emissions, but China’s population is four times as large.
If everyone in the U.S. had the same per capita emissions as your average Chinese citizen, we’d reduce our emissions by 75%.
However, that would only slow the rate of increase in atmospheric CO2 by about 16%.
Frugal dependence on fossil fuels just won’t do it. The only option is to cut out fossil fuels entirely, starting with coal and heavy crude.
Anyone who claims otherwise is just ignoring the obvious. The carbon can’t be buried in the ground; you just have to stop burning the stuff.
If you buy a Prius and reduce your emissions by 50% and congratulate yourself on the good deed you are doing - well, sorry, that’s delusional. All you are really doing is keeping your gasoline bill a bit lower.
23 September 2008 at 8:11 PM
We appreciate people’s interest in this idea.
As one of the authors, I wanted to answer a question that has come up a few times, which is “why gallons per 10,000 miles?”. In short, we think any measure of GPM would help car buyers recognize gains in efficiency more accurately. Shifting to “gallons per 100 miles” would be a big improvement over MPG.
But we think there are a few advantages to gallons per 10,000 miles. Our main premise is that we’re trying to help people recognize efficiency gains at the time they’re buying a car—that’s the moment at which a car owner makes a commitment to a given level of efficiency for the next 5 to 10 years. Let’s help buyers see the magnitude of their gas consumption over longer (but realistic) periods of time.
As a concrete illustration, here are gallons per 10,000 mile levels, at 100 gallon increments, and the corresponding MPG levels (with rounding):
1000 = 10 MPG
900 = 11 MPG
800 = 12.5 MPG
700 = 14 MPG
600 = 16.5 MPG
500 = 20 MPG
400 = 25 MPG
300 = 33 MPG
200 = 50 MPG
We believe that thinking in terms of gallons per 10,000 miles during the car purchase decision helps in the following ways:
It is a distance that is close to what many people drive in a year’s time and makes total gas use for a year salient (it directly quantifies the wastefulness of the inefficient cars and helps buyers think about cost and payback).
The base is round, which makes it (reasonably) easy to scale up or down (and preferable to other large, realistic distances such as 12,000 miles or 15,000 miles).
And, most importantly, it makes savings in gas between two vehicles large and obvious. For example, the MPG gain from 16 to 20 looks small, as does a gain in gallons per 100 miles from 6 to 5. But stating the improvement as reducing gas use from 600 gallons to 500 gallons is large and clear. That 100 gallon savings is about $400 and a ton of carbon.
We think having gallons per 10,000 miles on car stickers, at Consumer Reports, and at fueleconomy.gov would reach buyers at the right time in the decision process.
Following up on a few of the earlier comments:
More metrics–such as cost/mile and CO2/mile–would be extremely helpful. This reinforces the shortcoming of our current reliance on MPG–MPG isn’t directly useful for knowing gas consumption or its consequences(cost and CO2) without more calculations.
The ultimate goal, proposed by an earlier commenter, is to have a single meaningful CO2 metric for comparing a range of activities (driving, flying, upgrading an air conditioner, reducing meat consumption, etc.).
23 September 2008 at 8:48 PM
I think it would be great to see a ZipCar type concept on a larger scale, and for renting pickup trucks and SUVs rather than just compacts. Or maybe just some community cooperatives. It will become more difficult to borrow one on occasion once all my friends downsize. Daily rentals from large companies are too expensive, and the taxes are ridiculous.
23 September 2008 at 10:00 PM
in addition to the comments on #23 - I have a prius in Canada where all the gauges are in liters per 100km and a friend recently bought a new prius from the States so all the gauges are in mpg. It seems to me (maybe just the bias from looking at it for so long) that having an absolute bottom of zero and the linear y axis makes it far easier to discern relative difference in efficiency - filling up the entire top quarter of the guage from 75mpg to 100mpg is only a small change from 3.13 l/100km to 2.35 l/100km (assuming google has done my math correctly… using the correct gallons.)
Just another small reason to change it.
23 September 2008 at 10:09 PM
> moment-o-meter
(website)
> “… In-house tests CONFIRMED THAT the USE OF moment-o-meter
> MPG PLUS® AVERAGES 20% to 50% FUEL SAVINGS …”
I’d like to see your data, and your analysis. Will you provide these?
It sounds like you’re asking $250 for information I can get with a bobblehead doll on the dashboard.
23 September 2008 at 10:16 PM
Perhaps it is time for the United States to get into the 19th Century and go metric. In Australia we measure consumption in Litres/100 km. Makes a lot more sense.
23 September 2008 at 10:32 PM
Re ouini @21: “If the driving distance is 100 miles for a person in a 25mph car, then the driving distance might only become 110 miles for a person in a 46mph hybrid.”
Then again, it might not. Our annual milage went down when we sold our 10 year old Subaru and bought a Prius.
24 September 2008 at 12:55 AM
10 Samson, because 10,000 miles is a year’s worth of driving. I think 1,000 is better, though, since folks usually budget by the month.
17 mugwump (ahh, an appropriate BS in Humour name) I’m guessing you own TWO vehicles. Your argument fails miserably, even without the rental option.
19 Karen, the Hummer VS Prius spin assumed that GM’s vehicle would outlast the Toyota by perhaps 3 to 1 (they took the battery guarantee as the date the whole car would fry, yet strangely, didn’t take the Hummer’s guarantee for fry-time, even though GM products fry far faster than Toyotas.), and included tremendous fake recycling costs for the Toyota. (The Prius is built to make recycling easy, and Toyota gives a $200 refund for returning the battery.) The spin doctors then took the development cost for a hybrid system and leveraged it onto the few Priuses that had been built by then. The whole “analysis” was a pack of lies. Turns out 3 year old Prius resells for near its original price while the Hummer loses 54%! Turns out Toyota is making money off the development by spreading it throughout their line and also selling the tech to Nissan.
21 Ouini, you’re right. That’s why gas prices must be artificially inflated. Another way to do it is a $10 a gallon tax, with all proceeds refunded equally per adult legal resident. Ya don’t burn gas, you get free money. Cool, eh?
23 Gavin, I agree. I wonder when someone will come out with a video game with that premise. Pick different drivers (Little Old Lady, Eco-nut, Speed Demon), and score based on different parameters. Eric, I doubt displays cause a net increase in accidents. Folks get in the habit of leaving lots of space between themselves and other cars to allow for coasting. And accidents would be more :boinks: than ::BOOMS::.
30 Larry, add in lives saved, wear and tear, and the fact that cruising to tunes is better than slaving in a cube, and driving a bit slower makes ECOnomic sense. Plus, it’s “found” money (no taxes) and you save time by not pumping gas as often. A chip in the car that communicates with the speed limit signs would save lots of lives and gas. Speed limit is 65? Your car CAN’T go faster and society stops wasting gas on cops. OTOH, plenty of folks adore the rush given by pounding 300 ponies to their limit.
31 Figen, Airplanes can’t be hybridized (though I guess a 4 engine plane could have two tuned for efficiency and two for power, with the power engines turned off during cruise), but either inclined runways or launching vehicles could reduce the size of engines needed. Some safety reduction would result, and folks have shown an amazingly intolerant view of air-danger when considering their flip attitude towards car-carnage. Cars that increase danger are coveted!
24 September 2008 at 4:08 AM
Speaking from the UK, another problem with gallons is that the US gallon is only 0.83 of an Imperial (UK) gallon. In the UK, where we still think in mpg, this has led to a widespread belief that US cars are incredibly inefficient and a sense of self righteousness that Euro cars are greatly more efficient. It’s not particularly true.
24 September 2008 at 4:50 AM
re 7, 39, diesel-gasoline comparison, other emissions (!)
1 gallon diesel leads to 15% more CO2 emissions than 1 gallon gasoline.
diesel engines are about 25% more efficient in fuel use (litres per 100km)
Thus: if you just compare the litres per 100km of a gasoline and a diesel car, you have to add 15% to the diesel number to get a comparison of CO2 emissions.
If you focus on a certain type of car, CO2 emissions are about 10% lower (25% less fuel use, 15% more CO2 emissions) for the diesel car.
But: CO2 is not the only thing! A diesel car without particle filter emits in the order of 100 to 1000 times more particulate matter (which is not a good thing) and about 3 times more NOx (which is a precursor of ozone) than a gasoline car with catalyst.
Thus: When chosing between diesel and gasoline, do not forget the lungs of the people around and only take the diesel if it is with particle filter.
These numbers are for the Swiss car fleet, but probably is not very different from other countries (we have no car industry of our own…)
24 September 2008 at 5:00 AM
re 17
I’m with you, man. We got rid of all our cars and cycle everywhere now. Just strap a kid to each thigh, one across the pannier racks and another on my back and we’re away (I only make the wife carry one kid).
Not so stupid - I visited friends over the weekend (by bike and train) My friend gave me a lift to the rail station on his school run. We cycled in on a triple (him on the front, me in the middle and his daughter on the back. Strapped my rucsac on the back on top of the paniers - worked fine for the 10 miles into town. I commute by bike myself 15 miles eachway. I save the car for longer journeys or where I have too much gear for the bike. So far this year I’ve saved 2200 miles by commuting on the bike.
24 September 2008 at 5:09 AM
Your calculation is of course correct, but in general it makes more sense to get the most mileage out of your liter/gallon. Driving SUVs is certainly fun but I suppose 90% of the poeple using them do not need them. Here in Europe we have a growing tendency to of using bicycles and public transport for short distances. A recent study showed that the average distance people travel in their cars is less than 5 kilometers.
The other bloggers are right of course that it is difficult for the public to compare different fuel standards. But the real message we should get across is: only use your car when you really have to. i guess that could save a huge amount of CO2 emissions, regardless of the mileage per litre of fuel.
24 September 2008 at 7:16 AM
RE #42:
Why is a bigger car wasteful and inefficient?
And I doubt you want people thinking too deeply about that cost and payback. Most hybrids have a much higher total cost of ownership than their purebred cousins.
24 September 2008 at 8:10 AM
Doesn’t driver A only reduce their fuel consumption by 33 percent, while driver B reduces their fuel consumption by 45 percent? Sure, driver A reduces their consumption by 2.2 gallons per 100 miles, but they are not reducing their fuel consumption (on a percentage basis) as much.
It is my opinion that Driver B made more of a sacrafice.
24 September 2008 at 8:41 AM
I did 90 miles yesterday in a Audi A3 2.0 TDI and got an average of 60.2 MPG. As the average MPG in the USA us 22 MPG and only 33 MPG in Europe there is a lot of scope for improving liquid energy use but a lot of people probably need to start walking again.
24 September 2008 at 8:50 AM
Another variable that would be considered when building a “more efficient” fleet of cars is the market size. Right now, the SUV market is tumbling. In a few years, increasing the SUV efficiency may only affect a few people whereas increasing the Camry efficiency would make a dramatic impact on overall fuel usage.
Oh, and I personally like the gallons per 100 miles. I can relate to 100 miles. 10,000 miles is a bit too abstract unless you’re sitting down and looking at yearly expenses (which sadly too few of us do).
24 September 2008 at 9:47 AM
Re #17: though your tongue was clearly in cheek, allow me to point out that while cycling (and walking) can easily be superior to vehicular transport in CO2 emissions per passenger mile, it depends on the diet that produces the energy used by the muscles. The Pacific Institute has studied this; see http://www.pacinst.org/topics/integrity_of_science/case_studies/driving_vs_walking.pdf.
24 September 2008 at 10:47 AM
I like the gallons/mile (or 1000 miles or 10,000 miles) idea. I do own a large SUV for business needs. As gas prices skyrocketed the last year and a half, I took the concept one step further and began thinking in terms of $$/mile. As in the 33-mile trip to the jobsite is going to cost me ~$8. It definitely helped me focus on the necessity of a trip and looking at ways to combine multiple travel needs to reduce my overall expenses.
Maybe in addition to gallons or liters per mile, efficiency should be posted in $$/year, assuming some standard yearly mileage, e.g., 12,000, and whatever the average price of gasoline is for that quarter.
24 September 2008 at 10:53 AM
I don’t believe that there is any emission reduction in both cases.
The cumulative emissions will depend on the extraction of oil, not on the MPG.
Of course you can drive more miles per gallon (or per $) with a car with a higher MPG value. But this is an economic benefit.
To reduce the (cumulative) emissions we would need to keep some oil or coal in the ground.
24 September 2008 at 11:50 AM
It is a mistake to ignore the upstream costs of fuel production, measured as energy input and CO2 released.
Thus, one should compare the energy demand for gasoline derived from crude oil to that of gasoline derived from tar sands oil to that of ethanol and biodiesel derived from biomass.
Ignoring the life-cycle analysis is not at all justified, and is highly misleading as well.
24 September 2008 at 11:58 AM
has anyone figured out a way of measuring how much oil (carbon) is used in making a car?
24 September 2008 at 12:15 PM
Any gasoline powered vehicle can be easily and cheaply converted to run on compressed natural gas or propane. I’ve had the Jay Storer book for 20 years.
http://www.amazon.com/s?ie=UTF8&keywords=Propane&index=books&page=1
We could create a network of conversion shops (think muffler shops) across the country. How badly do we want to get away from foreign oil and use domestic natural gas?
24 September 2008 at 12:23 PM
Well mugwump shows in #53 how little he thinks if that thinking may point out his lifestyle to be wrong in ANY way.
Muggers, when you’re driving a 3L SUV you’re driving yourself and a ton of extra car that isn’t needed to carry you forward.
A smaller car is still more than ample for carrying you where you wish to go.
24 September 2008 at 12:47 PM
Re. Mugwump, #53:
This is disinformation - see here.
24 September 2008 at 1:38 PM
53 mugwump claimed, “Most hybrids have a much higher total cost of ownership than their purebred cousins.”
Totally ludicrous. In 2008, 55% of all hybrids sold were Toyota Priuses. So that single model represents MOST hybrids. A 2005 Prius (private party 40k miles) sells for around $21k, That’s $2300 total depreciation for a car four model years old! Add in gas savings, and it’s a slam dunk. Drive a hybrid, save tons of cash.
61 Robert, http://www.pacinst.org/topics/integrity_of_science/case_studies/hummer_vs_prius.pdf “The British auto industry trade group estimated in their 2006 sustainability report that life cycle CO2 emissions – a strong proxy for energy – are allocated 10% to manufacturing; 85% to use; and 5% to disposal.” Note that the 5% for disposal is overstated, and could be a negative carbon cost, since the results of the disposal is raw steel, etc, which eliminates the need to mine and refine more steel.
24 September 2008 at 1:48 PM
Reply to Hank Roberts.
You wrote: > moment-o-meter
(website)
> “… In-house tests CONFIRMED THAT the USE OF moment-o-meter
> MPG PLUS® AVERAGES 20% to 50% FUEL SAVINGS …”
I’d like to see your data, and your analysis. Will you provide these?
It sounds like you’re asking $250 for information I can get with a bobblehead doll on the dashboard.
ANSWER: It took us 3 years to succeed to display the momentum of a vehicle and you want believe you cab=n do it with a “bobblehead on you dash board”. I give you a free Moment-o-Meter if you prove me you can do it. Our data are backed up with a money back guarantee.
Tom Delor, Inventor.
24 September 2008 at 1:48 PM
#57: for the link to work, remove the trailing period.
24 September 2008 at 1:53 PM
I drive an electric car with a 6KW AC traction motor and 6 220AH 12 Volt gel cell batteries. Even with the DC to AC conversion its still quite efficient and I get speeds up to 55MPH. At $19K costs less to buy than a Prius, and the lead batteries can be completely recycled.
I have a solar array to charge it partially, though I still connect to grid while at work.
Perfect for everyday around town…cost to operate per mile, including, cost of grid electricity and battery replacement every 4 years is less than 5 cents per mile.
24 September 2008 at 2:26 PM
Mark - #34
No, it’s not opportunity cost I’m talking about. Do you think drivers are thinking of arriving at their Dilbert jobs earlier so they can get to work earlier?
Not me. But beyond that, a lot of people driving on the freeways are not commuting. Yet, they are still resistant to slowing down even to the speed limit. They are simply impatient. They need incentives to slow down.
My point is that not enough thought has been given to the question of what will influence people to change their driving habits. As many posts here have shown, it is a fertile field, and there are better ways than giving mpgs, the knee-jerk response. It has been suggested that some form of gpm, e.g., would be better. I think so. Maybe dollars saved per gallon. But not what they are being paid per hour to slow down because the wage is too small. People might be moved by $50/hr, but not by $9/hr. Who is motivated by minimum wage?
Others have suggested to me that dollars saved per 100 miles would be more meaningful because it is how much will he save on a specific trip that matters to the driver. It would be relatively easy to scale up or down from 100 miles, easier than figuring out the trip savings from an hourly “wage” which is a two-step calculation.
Or, knowing that people will drive 5 miles out of their way to get save 2 cents/gal, perhaps the effective reduction in cost of a gallon of gas would be persuasive. I don’t know. I do know that a lot of people are driving with no apparent consideration of the effect on mileage.
I have tried driving the speed limit on recent trips of 3500 miles (RT) and 2000 miles. This is now possible as trucks have mostly slowed to the speed limit or just below (at least in the center of the country where I was driving - the Mississipi R to Arizona). So they have discovered the savings in lower speeds. It was relaxing to settle in the righthand lane with the trucks and let others jockey around each other and the trucks.
And yes, Mark, I wore incontinence pull-ups as you suggest I should. I recently had prostate surgery and am still on the road back.
24 September 2008 at 2:31 PM
Re Ike Solem @41: “Frugal dependence on fossil fuels just won’t do it. The only option is to cut out fossil fuels entirely….If you buy a Prius and reduce your emissions by 50% and congratulate yourself on the good deed you are doing - well, sorry, that’s delusional. All you are really doing is keeping your gasoline bill a bit lower.”
Ike, unfortunately, for the time being we’re stuck with the infrastructure we have, and one can not currently buy a fossil fuel-free car. Until one can, the Prius is an interim step that at least uses less fossil fuel.
Captcha: warning send
24 September 2008 at 3:23 PM
Jim Eager, I would instead recommend holding off on the purchase of any new car whatsoever until the electric and added-range electrics (i.e. an electric with a internal combustion engine for charging the battery) are available.
Second, consider the fact that tar sand crude oil generates around 35% more CO2 emissions per gallon of gasoline than does conventional crude.
However, it does appear that a few of our politicians are aware of that issue:
Edmonton Journal, Canada, Sept 16 2008
Such laws should be extended to ban the import of tar sand oil to the United States, period.
24 September 2008 at 3:55 PM
That’s what I’m doing, trying to nurse my 1990 Acura to at least 275K miles before replacing it with some form of plug-in/internal combustion engine combination.
24 September 2008 at 3:58 PM
To clarify:
http://www.salon.com/comics/opus/2008/07/06/opus/
24 September 2008 at 4:09 PM
What’s best? Swapping your SUV for the prius! C! Or maybe not. Steve Koonin - Chief Scientist BP claims that US car engine efficiency went up 23% in the decade 1990-2001. Americans responded by buying heavier vehicles and driving more. Result - more fuel burnt.
http://uk.youtube.com/watch?v=wt_mluFK7xk
Plenty of food for thought in this clip.
OK - public transport D or bike E.
24 September 2008 at 4:54 PM
RE #71 & “tar sand crude oil generates around 35% more CO2 emissions per gallon of gasoline than does conventional crude”…
I was wondering if either the tar sand crude or perhaps some types of biofuels might actually entail more energy (measured in calories or BTUs) in their production than the energy (calories or BTUs) gained from them. If such endeavors are being heavily subsidized, it’s possible that could happen, and people would be subsidizing boondoogles, not to mention grossly harming the environment.
Of course, ALL energy input in the process of production would have to be accounted (including workers driving to work and eating), not only the more obvious and direct energy used.
I know this sounds preposterous, but, well, it could conceivably happen.
24 September 2008 at 5:20 PM
> Our data are backed up with a money back guarantee.
> Tom Delor, Inventor.
Yeah? I’d like to see your data and your analysis. Where can we look at the data and the analysis?
I’d like to see exactly what is in this data that you say is backed up by a money back guarantee.
24 September 2008 at 5:23 PM
According to an IEA paper, in 2005 CE the world produced 5.9 billion tonnes of coal, two-thirds of that for electric power production.
That’s a lot of CO2 every year.
24 September 2008 at 5:32 PM
Larry, #69.
So how is “wasting” 5 minutes a day in traveling to work costing them anything? The work schedule isn’t 100% full and 5 minutes out of a 10 hour day is 0.83%. The work schedule isn’t timed to achieve 100% efficiency. They cannot “sell” 5 minutes of their time for ANY amount.
So how, in any sense of the word “earn”, would they lose any money by taking five minutes longer to get to work at their hourly base rate? Or even minimum wage?
24 September 2008 at 7:15 PM
Re #42
This is an important thing to get right if you want to dislodge mpg.
I understand your motivation for using gallons per 10,000 miles, but I think that gallons/100 miles is a far easier figure for average drivers to comprehend (and slightly easier to calculate).
Most drivers probably (IMHO) don’t keep a close tab on how far they drive in a year, but they are aware of how far any of their regular round trips are (20 miles, 50 miles etc) and the gallons/100 miles figure is on the same scale. They can easily figure out what their existing gallons/100 miles figure is, which is important when they come to compare with the efficiency of a new vehicle.
Determining gallons/10,000 miles sounds like too much math[s].
Test it out, it would be a shame to not displace the mpg metric just because you picked a big number.
Andy
24 September 2008 at 7:35 PM
Urs Neu #50
Thank you for yor clarification, it puts clear solid figures to my vague statements. However I feel that:
“But: CO2 is not the only thing! A diesel car without particle filter emits in the order of 100 to 1000 times more particulate matter (which is not a good thing) and about 3 times more NOx (which is a precursor of ozone) than a gasoline car with catalyst.”
Is not an honest comparison, firstly because it is not fair to compare unfiltered diesel emissions with petrol emissions submitted to catalytic filtering process. Comparisons must be like with like in order to be valid. And would even challenge you to find automobile markets where the regulator (introduction of such devices is never a result of a “free market”) imposes catalysts in petrol without imposing filters in diesel.
Comparing like with like, the total amount of toxic polutants is equivelant in both engines, with the difference that petrol emits mostly small particulates and diesel emits mostly large particulates, these will have impacts different points of your respiratory organs but remain nevertheless toxic and carcnogenic, in other words, different flies…
Cheers.
24 September 2008 at 7:36 PM
Re Ike Solem @71: I would instead recommend holding off on the purchase of any new car whatsoever until the electric and added-range electrics (i.e. an electric with a internal combustion engine for charging the battery) are available.”
Ike, I would agree with your recommendation if I were thinking about replacing a vehicle and there was no compelling reason that I had to buy sooner, but we bought our Prius a year and a half ago to replace a 10 year old car with 200k on it and doubled our mpg, and I have absolutely no regrets.
As for thinking about gasoline source, how exactly is a consumer to know where the source crude came from when they pull up to the pump?
24 September 2008 at 8:29 PM
Mark #78
Either I am doing a lousy job of explaining what I mean, or you are not paying attention, Mark.
Who said anything about the driver “wasting” time. You did, not me. It’s your term, not mine.
The sense in which I am using “earn” is the ordinary, garden variety sense in which you get a return for the investment of your time. Just like in most everyday situations, the time spent in earning that money is not, repeat NOT, in competition with other ways you might spend that time, unless as you point out the boss is unusually time-on-job conscious.
No, the sense of “earn” here is the same as getting a return for clipping coupons and redeeming them at the grocery. It is not in competition with other ways of earning money so there is no opportunity cost…nor is there any OC in driving more slowly (ordinarily: but if it would make you late for an appointment with the President, all bets are off). But again, Mark, most driving does not even involve commuting, so can we quit talking about arriving five minutes late to work? By driving more slowly, no matter the destination a driver saves money, which is indistinguishable from earning money (except no taxes!) for the extra time spent on the road. That’s it.
Once again, the real question is what would motivate drivers to slow down. I would love to hear your thoughts on THAT.
24 September 2008 at 8:55 PM
If congress is mandating efficiency standards, they could easily also require all cars to have fuel use monitors. Our European turbo diesel has one, and we generally ‘video game’ it to try to stay under 6 l/100k (39 mpg) in town and 5 l/100k (47 mpg) on the road.
Obviously liters aren’t directly comparable, since diesel has both a higher specific gravity and a slightly higher C-H ratio.
24 September 2008 at 9:04 PM
The same point was made on GreenCar.com a while back, in an article attempting to defend the “need” for huge SUVs. My reaction is that if someone who is concerned about emissions feels a “need” for an unnecessary, overpriced status symbol like the Chevy Tahoe, they’d be much better off buying something like diamond jewelry (fair-trade, of course), which emits no carbon dioxide at all when kept away from very hot flames.
24 September 2008 at 11:28 PM
Gavin in #22:
Dean (#56) makes the crucial point. It is really the ubiquity of the low efficiency vehicles that make them a better target for first improvements. There are military reasons to improve the fuel efficiency of the Bradley Fighting Vehicle so that supply line needs are reduced, but there is not a big CO2 emissions urgency even though they burn more fuel than an SUV.
The fighting vehicles are rare so they can’t contribute much.
If SUVs become rare, then we want to look elsewhere. Ultimately though, we need a way to leave carbon in the ground. Shifting off of carbon entirely is more important and it is encouraging that one of the car manufacturers is planning to introduce a plug in minivan soon: http://www.bizjournals.com/losangeles/stories/2008/09/22/daily25.html
25 September 2008 at 12:53 AM
I think the best way to educate the consumer would be a meter on the dash that showed $ of gas used that day for the first few seconds the car was on, followed by a trip cost that measured the cost of gasoline used since the car had been started. When the car pulls into the gas station, the prices are downloaded to the car via bluetooth (which is already in many new cars).
Most people see fractions, energystar ratings, etc, and just tune out. They don’t want to be bothered with these things.
25 September 2008 at 1:01 AM
We are dealing here with a threat that is gradual and a long way off compared with our Fight or Flight response. So it has to ba a very solid wall folk need to come up against to change driver behaviour. Speed limiters will make people slow down, like Lab Lemming probably has on his euro diesel, and we have on our Citroen C4. Set (using a transponder) the limiter at the city limit to 30 kph, and on the open road to 80 kph and the country would immediately meet its savings target, and crank it down as things get worse. Draconian, maybe, but the alternative is to go without.
Good to see this discussion happening, and for most of us non-USA types its faintly amusing really, as we’ve had this ‘confusion’ resolved some decades ago! But feel free to catch up anytime!
25 September 2008 at 1:48 AM
I understand why lifecycle analysis wasn’t included because this article is making a simple point. But since since there is a lot of disinformation out there, some repeated here, an article on this topic would be good. In particular, I find it boggling that people are gullible enough to believe that engineers with a sharp environmental and energy-saving focus would neglect to do lifecycle analysis. It’s a whole lot more likely that engineers without either focus would neglect to do this.
In the meantime the WikiPedia page on Net Energy Gain may interest some though it needs some work at time of writing.
25 September 2008 at 3:18 AM
Larry, 82. No, the attempt to say “your five minutes spent extra is less than the minimum wage” only makes sense when you’re trying to show that they are wasting this time.
If you’re thinking about the money you could make, then you can’t sell your time in five minutes.
If you mean that the time could be spent in something else, well, the best way of getting time back isn’t driving faster to work. Instead of driving forty minutes fast, get a job that’s closer. You could save forty minutes a day.
Basically, I don’t understand why you are trying to work out the “wage” of driving slower.
25 September 2008 at 3:23 AM
Further Larry.
Why compare it to the earnings of “cutting coupons”? Cutting coupons isn’t “a job”. Anything you earn is because you bought the product. Cutting out 150,000 coupons for 10p off “feminine products” will save a single man exactly nil pounds. If they wanted to spend their time playing games or on their hobby then they don’t think “this will cost me $150 for the evening!!!” nor even “I could be saving money by cutting coupons for 25p off a pot of jam!!!”.
Your “point” has nothing to say about why you aren’t saving money by driving slower to work each day. Nothing relevant anyway.
25 September 2008 at 5:55 AM
mugwump writes:
1. Kinetic energy is:
Ek = (1/2) m v^2
where m is mass and v velocity. To accelerate a car to a given speed that masses twice as much, you need twice as much energy.
2. Air drag is:
D = (1/2) rho A v^2 Cd
where rho is density of the medium, A cross-sectional area, v velocity, and Cd the coefficient of drag, which varies with shape. Other things being equal, a car with twice as much cross-sectional area will exert twice the drag force, requiring twice the energy to overcome the drag force.
25 September 2008 at 7:00 AM
In Australia we use litres per 100km along with the rest of the metric system. We changed from the old Imperial units in the early 1970s.
Why wont the US make the change? Come on in the waters fine! And life is so much easier and more logical.
25 September 2008 at 7:07 AM
Mark,
Geez! I’m not talking about driving to work.
You don’t get it. No one else is interested. I give up.
25 September 2008 at 8:46 AM
Ike (71), what is “synthetic” fuel that Waxman prohibited from imports? Oil from tar sands? Refined gasoline from oil from tar sands? Did the referenced section ban such from only Canada, or did it ban such imports from anywhere?
25 September 2008 at 9:45 AM
The idea mentioned about putting mpg (or other measure) display on a dashboard has been recently made in one of the car magazines I read recently (Automobile? Car and Driver? I’m afraid I don’t recall.) But his point was that Prius drivers tend to pay attention to it because it’s understandable and it’s displayed, while Hummer drivers have no such display.
Interestingly, there’s been a similar push in the electric utilities. Most people don’t really have any feedback on how much power they’re using until the bill comes at the end of the month. The new idea is to try to give users of electricity some kind of usable way that they could be more aware of their own usage, and take steps to manage it.
Ultimately, perhaps, the most useful display for either vehicles or homes might be a $/day (or whatever local currency might be useful) to make it extremely concrete even for those who might not otherwise care much about NOx emissions or kW demand.
25 September 2008 at 10:30 AM
Just curious, did the used vehicle disappear? At my local most excellent taco stand (seriously, the best tacos on the planet and I am always the only white guy there) I’ve noted a trend. The parking lot is full of Escalades and Hummers. Used SUVs have become so cheap that immigrants are buying them like hotcakes. Last year I decided that since I drive my Honda Pilot so little, around 5000 miles per year, that it was best to just keep it. If I trade it, it’s likely the new owner will drive it a whole lot more. Our other car is a Civic. Throughout our marriage we have always selected places to live that are very close to work (no more than 15 minutes on city streets), and have always had one car that will haul the family on long vacations, and one car that gets high mileage. I know people look down on my SUV, but at the end of those noses there are a lot of people who have racked up a whole bunch more CO2 because of where they’ve chosen to live.
25 September 2008 at 10:44 AM
#84: Prof Bleen The same point was made on GreenCar.com a while back, in an article attempting to defend the “need” for huge SUVs.
The SUV won’t go away. In fact, alt energy is a certain way to increase the proliferation of large cars. The cost for energy has fallen at amazing rates over the last 200 years, even when $150/bbl oil is factored in. There is no reason to expect the cost of energy will not continue to fall at amazing rates. Nuclear, wind, locally generated solar, etc, will all play a role.
If moving to electric allows me to reduce my operational costs by 80%, and if my monthly energy budget stays the same, you can bet that driving larger and even more luxurious cars is coming. When gas prices rise, they drive less. When energy prices fall, they drive more. When energy costs tumble, they get a new car.
Build more roads. They will be needed. Increase the sprawl. It will be demanded. In 30 years expect that electric “smart cars” will be able to travel in closely packed caravans traveling at 130 MPH with computers running the show. You can sleep or read while on these super freeways and you’ll only need to drive on the legacy roads.
Sprawl is limited today by time and energy costs. Those barriers will fall.
25 September 2008 at 10:49 AM
Re 80 Lowlander
“And would even challenge you to find automobile markets where the regulator (introduction of such devices is never a result of a “free market”) imposes catalysts in petrol without imposing filters in diesel.”
This is e.g. the case for Switzerland (and other European countries). Catalysts are mandatory here for about 30 years now, while particle filters still are not. Catalysts are much more common than particle filters, at least in Europe.
“Comparing like with like, the total amount of toxic polutants is equivelant in both engines”
This is new to me. A catalyst does not eliminate particles, as far as I know. I am not aware of any reports confirming this. I only have sources giving a factor of 100 to 1000 more for diesel, irrespective of catalysts. There is only one new technology for gasoline motors (direct fuel injection) which produces similar amounts of particles. What are your sources?
It is well known that diesel soot is very toxic and is also relevant for climate (warming effect).
I agree for NOx which is about the same for Diesel and Gasoline without catalyst. The problem here is that there is a (very common) technical solution for the gasoline NOx but only first tries for the diesel NOx
Cheers
Cheers.
25 September 2008 at 10:54 AM
Collectively, substantial decreases in fuel use could be accomplished pending the replacement of the entire motor vehicle fleet. How about local traffic engineering depts making reducing idling time a priority in all planning. How about a cruise control which maintains throttle setting rather than speed. How about a reevaluation of the need for every overhead roadway light, and outdoor lighting in general for that matter. And on and on. What’s needed is that the issue be taken seriously and addressed simultaneously by all levels of society, from individuals right up through international organizations. Thanks to RC and all others who press the issue.
25 September 2008 at 10:59 AM
The original post and the whole discussion is not relevant to cutting emissions.
1. If you buy a car, you are supporting a massive industry that is committed to selling millions of vehicles to millions of people. A few mpg saved here or there is going to be wiped out by the fact that these companies want to sell more and more cars to more and more people across the world.
2. The primary issue with cars is that in order for them to be used efficiently, every seat in the vehicle has to be filled. But this effectively makes them into a pseudo public transport system where the owner/driver has to schedule journeys around other peoples requirements in order to make sure the emissions per passenger is the optimum minimum. The other consequence of this way of using a car is that far fewer of them would be required.
What do these two basic facts mean?
No matter how you view the subject, you can only reduce passenger transport emissions by operating scheduled services that are less convenient.
25 September 2008 at 11:48 AM
Re: Ed Beroset,
Green types have been calling for smart electric meters for some time now. Seeing what your usage is in real time, along with the associated cost, should lead to conservation. People would make a little game of it. One could directly see how much power an appliance draws whilst in “standby” mode.
There are some such toys available commercially, but even I (who would love to have such a thing) have balked at buying one - my spending on electricity is low enough that the payback period on the gizmo would be too long.
25 September 2008 at 1:01 PM
Matt (#97) and others are right, based on the evidence: when gas prices fall due to decreased demand or increased supply, people flee from the Prius and toward Tahoes. That is what happened over the past 20 years.
This is cause for deep pessimism. How will we as a nation reduce our gas consumption if, by doing so, we reduce prices, which leads inexorably to more consumption?
A related factor is that, by our unrestrained use of gasoline, we - the US - are causing an unprecedented, huge transfer of wealth from us to petrocountries, several of which are not our friends (Russia, Venezuela, Iran, even Saudi Arabia where some of the wealth ends up in unfriendly hands). This will have longterm effects on the relative strength and stability of nations, where the US becomes weaker and these countries become stronger.
So on the one hand we want high prices to discourage consumption, and on the other we want low prices to slow down the wealth transfer. Probably the only way to accomplish both goals, based on the evidence, is to increase the gas tax in this country. Of course, this is the third rail of politics in this free-the-consumer/driver society, but it is the only thing that has been shown to work.
Despite the weakening of the US by our short-sighted policies, conservative politicians are unwilling to do anything, maintaining the obvious fiction instead that we can drill our way to oil independence. Apparently, their professed patriotism is all talk. It is a stunning fact that they are willing to strengthen our opponents by sending our money to them instead of raising taxes to pay ourselves where we could do some good with it.
We have a clear choice: raise gas taxes dramatically and weaken Russia, Iran, Venezuela and the terrorists…or continue to do nothing, in which case we, but not our children and grandchildren, deserve what we get.
25 September 2008 at 1:16 PM
Rod B,
Waxman’s rule only applies to U.S. government purchases, much like the U.S. government is largely restricted to purchasing automobiles made by U.S. firms (at least, I think that’s still the case).
However, once the various gasoline components have been refined and purified, they are blended and mixed - so essentially it is impossible to keep the tar sand gasoline out of the conventional crude gasoline, as I understand it.
What is also remarkable about the Canadian tar sand model is how destructive it will be to Canada’s long-term energy and environmental outlooks.
Canada has a limited supply of natural gas, and much of it is now being fed into tar sand oil production. Natural gas is the cleanest-burning fossil fuel, with the highest energy release per carbon atom (due to the higher energy release on combustion of a carbon-hydrogen bond vs. a carbon-carbon bond; methane has 4 C-H bonds per carbon atom).
That leads to the standard phase-out rule: coal, tar sands and shale oil are the most polluting and have the least energy, conventional petroleum is in the middle, and natural gas is by far the best.
As far as the comments about cars in this context, the whole issue is ensuring that transportation is zero-emission. I think this particular post leaves out the major issues, though.
If we extend the argument presented, it becomes clear that the real savings will come at the trucking and agricultural equipment level. Those machines use mass amounts of fuel, and often get only 1 or 2 mpg. Electric trucks and electric farm equipment should thus be at the top of the agenda.
Furthermore, we need laws and regulations - there are no “free-market solutions” - for one thing, the global energy market is not a free market by any stretch of the imagination. In fact, it operates largely as a cartel system, with inordinate political power. It is very clear that as a result, the U.S. government regularly intervenes in energy markets to promote fossil fuels and suppress renewable competition - this goes on at the academic level, the Congressional level, and the Executive level (i.e. DOE, NSF, etc.).
The proof? Billions in credit guarantees for fossil fuel energy projects, and not even a stable renewable energy tax credit for renewables - let alone credit guarantees for renewable energy projects.
This even extends to intervention in climate science projects to suppress data collection that would clearly demonstrate what’s going on. Here, we are talking about NASA and its director, Michael Griffith, who have refused to launch Triana (the Deep Space Climate Observatory) for about a decade now: http://www.iht.com/articles/2006/01/15/opinion/edpark.php
Griffin is something else - he claimed today that “space exploration is critical to humanity’s survival” but he won’t allow the most important climate satellite ever devised to be launched:
http://www.space-travel.com/reports/Space_exploration_key_to_mankinds_survival_NASA_chief_999.html
What is the guy saying - let’s trash the Earth to the point where it won’t support our global population, and then go find “somewhere else?”
That’s bad science fiction in the tradition of Michael Crichton, not responsible administration of the U.S. space agency. What a nightmare.
25 September 2008 at 1:41 PM
In response to the question of the ‘pay’ for driving slower to save gas, maybe this answers the question.
1 Assume 10,000 miles per year of driving (just to use a round number).
2 Compare two speeds: 65 MPH and 60 MPH, and assume my 10 % increase in MPG can be generalized.
3. At 65 MPH, I would drive 10000 miles in 154 hours. At 60 MPH, I would drive 10000 miles in 167 hours. Time difference is 13 hours.
4. In my case, at 50 mpg, I consume 200 gallons and at 55 mph I consume 182 gallons, for a savings of 18 gallons. My last fillup was at a cost of $3.50, so I would save $63 in 10000 miles. $63 / 14 hours gives a ‘pay’ of $4.85 per hour.
5. Let’s assume I drive a vehicle that will achieve 20 mpg at 65 mph and 18 mpg at 60 mph. In this case, I go from consuming 555 gallons (18 mph) to 500 gallons (60 mph). Again at $3.50 per gallon, I would save $193 over the 10000 miles. $193 / 14 gives a ‘pay’ of $13.75.
Thus, the hourly value of saving fuel depends on your fuel consumption, which ties in to the original post. Thinking of fuel consumption in terms of fuel per mile is more constructive than thinking of fuel consumption in terms of mile per unti of fuel consumed.
However, there is ‘hidden pay’ that will be gained by using energy more efficiently. The clear benefit is enjoying a lower energy bill. The hidden benefit, if all aspects of society focused on energy efficiency would be lower oil consumption, which would result in lower energy costs (supply / demand) and reduced emissions of greenhouse gases and other atmospheric pollutants.
If we can reorient our cultural thinking towards energy efficiency, we may make more progress on developing effective public transportation in more regions of the country, better physical fitness (perhaps) if people walk more and drive less, etc etc.
25 September 2008 at 2:25 PM
I wonder how relevant this is in terms of global impact. Lets assume the US would gradually reduce their average mileage to current european levels over the next ten years (ambitious when taking into account how many cars already exist that can’t simply be swapped, especially in times of financial cirsis) - how much would that reduce glocal co2 emissions?
25 September 2008 at 2:27 PM
There I said it: “reduced”. I meant “increased”, of course. We’re talking about consumption here in europe, where “less” is “less” and not “more”. Sorry for the confusion.
25 September 2008 at 3:46 PM
oxnardprof (#104): I think your calculations and conclusion are good. One thing I would point out, is comparing those two speeds might give people the wrong impression.
My usual vehicle is a 2000 dodge mini-van. It has the fancier “driver info center” that lists instantaneous mpg, engine running time, and average vehicle speed. I was skeptical of the accuracy when I first used it, but it really seems quite accurate. I was very surprised to find that my average speed (after driving for a week) was about 32MPH. I live 20 miles out of town, so most of driving is at 50-60MPH on rural highways - or so I thought! My conclusion is that slowing down 5MPH would be almost unnoticeable.
And I have generally been driving slower. At 75, I might get 19mpg. At 65 it might improve to 26mpg. (didn’t seem to help much going down to 55) My favorite is drafting behind a semi, can get 35mpg that way, but it is hard to come across that situation.
25 September 2008 at 4:13 PM
I have a small Honda Civic which is a pretty efficient car, but I have to admit I drive very fast when I can. I’m in the Midwest, God’s great open spaces and all that.. It is very seductive if you want to drive fast. Though i know better intellectually, I keep being tempted by the notion if the road is open, why not just go? But I am being humbled and embarrassed by my driving habits as this discussion is progressing and even thinking of changing my ways
25 September 2008 at 4:46 PM
#102 and others - as well as price mechanisms, another way to reduce carbon emissions from cars is to… well, reduce the carbon emissions from cars. This is what the European Union have done today, in a surprise and very bold move (http://www.bbc.co.uk/blogs/thereporters/markmardell/2008/09/blow_to_carmakers.html). And following the recent stock market madness, regulation may not be as dirty a word today as it has been for the last 20 years or so…
Great though all this increasing efficiency tinkering is, it is clearly nowhere near enough though. The only remotely effective response would be to ban all new petrol and diesel cars in about 10 or 15 years time, and all existing fossil fuel cars on the road given no more than another 10 years after that (parallel with colossol low-carbon electricity expansion). And all that really needs is legislation and plenty of warning so companies can adapt and a new infrustructure can be put in place.
Easy, eh?!
25 September 2008 at 5:47 PM
You’re trying to get Americans to switch to different units?! Good luck with that.
In NZ we switched to the metric system (or that’s what we called it) a few decades ago. People are quite comfortable with distances in km and buying petrol by the litre, but still tend to talk about fuel consumption in miles per gallon. If they don’t, they use km per litre. The official unit (litres per 100 km) is considered unintuitive.
And NZers are much more adaptable than Americans!
25 September 2008 at 6:56 PM
I think we have much more serious and immediate problems than the main topic of this thread implies:
http://climateprogress.org/2008/09/25/global-carbon-emissions-jumped-3-in-2007/
despite an economic quasi-recession, despite small beginnings of greater energy efficiency, despite …
25 September 2008 at 7:17 PM
Gavin, I agree with your suggestion of a clearer statement of efficiency.
However, my concern is that there is an great opportunity for a much larger and fairly rapid improvement that could be lost. If we could reduce the CO2 emissions due to personal transportation by 90%, we would make a serious impact on the global warming situation. This is possible if high efficiency cars were to be adapted on a large scale. People seem reluctant to change how they ride in their cars, and if a sense of improvement such as you describe, (a) by trading in an SUV for a hybrid SUV, or (b) trading in a typical car for a Prius, will lead to complacency, can be accomplished with these part steps then people will not look hard at their current operating patterns. People will not change cars all that often, so we need to get this right.
Even worse, would be to trade in the SUV for the hybrid SUV that is a “plug-in” hybrid, or simply all electric vehicle. The electric power is really a carrier of power from central power stations, and due to economic reality and capacity of various types of power stations, this additional load will result in added coal usage. This will approximately make up for any possible efficiency improvement of central power stations compared to typical car engines. The net reduction in CO2 is not much, if any. And we are about to see $25 billion handed to the auto industry to do just that.
Unlike Guy (109) who would ban cars, I would prefer to make high efficiency cars that could keep us in our present chosen life styles, and still accomplish a nearly complete solution to the CO2 problem from personal cars.
25 September 2008 at 8:22 PM
There is too much error in this method of analysis. MPG does not reliably correlate (inversely) to emissions when comparing older to newer vehicles.
Many newer vehicles have low-emission engines, especially Honda, but also Subaru and others. The engine and exhaust technologies are so important that they could topple the winner chosen by using the comparison method suggested in the article.
Another factor in choosing a vehicle that will be low in emissions is how well the engine is able to retain efficiency between regular tune-ups. That is: what is the rate of decline in efficiency between maintenance cycles? Subaru and Mercedes will often beat GM and Chrysler in this area.
Further, proper maintenance of the vehicle is at least as important as what vehicle you buy. Something as simple as failing to keep your tires at the right pressure can reduce efficiency a lot (as well as ruin your tires’ substructure).
[Response: CO2 emissions are related to fuel usage not post-processing of the exhaust. You are correct in terms of NOx and CO, however. - gavin]
25 September 2008 at 9:09 PM
Regarding the concern that increasing the use of high mileage cars will lower fuel prices and people will then return to guzzlers:
Not so if the demand for higher mileage cars leads to economies of scales and the development of new technologies that enable electric cars with long driving ranges to be built at competitive prices.
No matter what petrol will not get cheaper than now. And even at the prices of a few years ago most people would not be vain enough to choose to pour money into a petrol driven car if there was comparable performance alternative.
25 September 2008 at 9:44 PM
Ouch, sorry about the crumby grammar in the last paragraph of my last post. What I meant is that reduced demand as people shift to more efficient cars may have an effect, but there is no reason why this would make enough people shift back to inefficient cars to bring demand and prices back to current levels. If the price of fuel was a quarter what it is at the moment, most people would still prefer not to pay it if they had a reasonable alternative.
25 September 2008 at 10:19 PM
Ike (103), thanks for the clarification. What got my curiosity up was the strange use of the word “synthetic” by Waxman. I wasn’t sure at all what he meant by that or if he knew what he was talking about.
I think you’re stretching the gov’t’s support for fossil fuels and their suppression of renewables way beyond the pale. I’m not sure what you mean by “Billions in credit guarantees for fossil fuel energy projects”; and your “not even a stable renewable energy tax credit for renewables…” statement doesn’t ring true. The gov’t pumps $billions into renewable research, development and support. If you’re referring to the needs-to-be-renewed tax credit for wind power, e.g. as not being “stable”, you have an accurate point, but it’s miniscule. T. Boone would not be investing $billions in a wind farm if he had the least indication that the production credit was less than 100% certain.
I heard someone is building a commercial all-electric train locomotive (though I don’t know exactly what “all electric” means); Do you know if this is accurate?
25 September 2008 at 10:26 PM
Figen, Midwest! Aah! God’s country. Kansas is the best for driving. Roads that go for tens of miles with no hills, curves or other cars.
26 September 2008 at 3:48 AM
Larry, this:
“Recently, I wondered how much one would “earn” as an hourly wage in terms of the money saved per hour of extra travel time due to the lower speed.”
Sounds like you ARE talking about how much you earn driving. It was soon after someone posted they drove slower and were five minutes later than normal.
If this isn’t about driving to work, why do you care about how much you’d “earn”? You’d not earn anything. You’d merely not have to spend (which is like finding free money), so it doesn’t matter if it works out do 5p an hour, that’s 5p for one hours “work” you had to do anyway and weren’t being paid for anyway.
Maybe you ought to explain why you wanted to do that calculation, put it up on this site as a comment and decry that it was barely minimum wage.
26 September 2008 at 10:31 AM
Mark: It is, in fact, fairly common procedure for economists to look at savings/unit time and ask “is this worth it?” Yes, this is an opportunity cost calculation, as you point out, but usually economists assumed that people value their free time at about their average hourly wage.
Obviously in the real world people do not calculate out every action they take in monetary terms, but I would argue this that this example is cleaner than most. 5 minutes longer in a car is 5 minutes less doing everything else I want to do. If it is a work commute, than that