Planes, trains and automobiles: Traveling by car uses most energy

Jan 10, 2014 by Bernie Degroat

(Phys.org) —Fuel economy must improve 57 percent in order for light-duty vehicles to match the current energy efficiency of commercial airline flights, says a University of Michigan researcher.

Michael Sivak, a research professor at the U-M Transportation Research Institute, examined recent trends in the amount of needed to transport a person a given distance in a light-duty (cars, SUVs, pickups and vans) or on a scheduled airline flight. His analysis measured BTU per person mile from 1970 to 2010.

He found that the entire fleet of light-duty vehicles would have to improve from the current 21.5 mpg to at least 33.8 mpg, or vehicle load would have to increase from the current 1.38 persons to at least 2.3 persons.

"It would not be easy to achieve either of these two changes," Sivak said. "Although fuel economy of new vehicles is continuously improving, and these changes are likely to accelerate given the new corporate average , changes in fuel economy take a long time to substantially influence the fuel economy of the entire fleet—it takes a long time to turn over the fleet."

For example, he says, the 14.5 million light vehicles sold in 2012 accounted for only 6 percent of the entire fleet of light vehicles on the road.

"A historical perspective illustrates the daunting task," he said. "An improvement of at least 57 percent in vehicle fuel economy of the entire fleet of light-duty vehicles would be required, but from 1970 to 2010, vehicle improved by only 65 percent."

Sivak says that the required increase in vehicle load—67 percent—would be even more difficult to achieve. Vehicle load has continuously dropped since 1970.

While the energy intensities of both driving and flying have steadily decreased over the last 40 years, the improvement for flying has been substantially greater than driving—74 percent versus 17 percent.

"It is important to recognize that the energy intensity of flying will continue to improve," Sivak said. "Because the future energy intensity of flying will be better than it currently is, the calculations underestimate the improvements that need to be achieved in order for driving to be less energy-intensive than flying."

Overall, in 2010, BTU per person mile was 4,218 for driving versus 2,691 for . Other modes of transportation: Amtrak trains (1,668), motorcycles (2,675) and transit buses (3,347).

Explore further: Saving gas: Less driving, better fuel economy

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Eikka
4.2 / 5 (5) Jan 10, 2014
"It would not be easy to achieve either of these two changes,"


Well it's already been achieved on the other side of the Atlantic.
ab3a
4.1 / 5 (7) Jan 10, 2014
The number of occupants per vehicle changes the complexion of this statistic dramatically, particularly for automobiles. The assumption is that we should try to be more efficient by putting more people in more vehicles.

However, those who drive work vans and pickup trucks typically carry cargo with them --not passengers. The goal in their case is to get to the job site with their equipment and spare parts.

The statistics behind this "study" assume the goal is to move people, not cargo. So in that light, private road travel looks bad. However, if you pack a family of five in a minivan, suddenly road travel looks incredibly efficient. The difference? One guy is hauling his work materials and the other is a family going to Grandma and Grandpa's house. There is no way to compare these activities. Furthermore, it is unlikely that Grandma and Grandpa live within walking distance of an airport, so airline travel is out of the question.

Feeble-minded studies like this make bad policy.
antialias_physorg
3.9 / 5 (7) Jan 10, 2014
However, those who drive work vans and pickup trucks typically carry cargo with them

Most of the time they drive empty (at least when I see them on the road). This also goes for the minivans.
In those casees a second car optimized for single person transport would increase efficiency a lot. However most people don't have money (or space) for two cars so they buy the biggest one they'll potentially need.

It's also an issue with population densities. Not everywhere does the integration of bus/plane transport make sense.

As for the article: 33.8 mpg seems very doable. I get 40-45mpg (40 for autobahn, 45 for mixed autobahn/city traffic) and my car is 10 years old.
Returners
2 / 5 (3) Jan 10, 2014
Well, I can say I dislike all the extra cab and extended cab full size trucks, especially in the parking lot, and no, you often don't see those carrying a load.

I totally understand ab3a's position (5 stars,) as it's another one of those situations where personal economics and macro-economics simply don't agree. For a contractor's point of view, they need a work truck, but they also need something that can double as a family car, so they get an extra cab truck. It also helps for carpooling workers. Yet if they are not using it for those purposes, extra passengers, it then becomes dead weight.

So if it's an actual contractor who actually uses the truck to it's full potential, or is using it for family transport when they aren't working, that's a good thing, but if it's just some guy who bought a big truck because they like big trucks, that's a waste IMO.

They can't just cut weight for fuel economy for trucks, because they haul loads, unlike cars.
Returners
2.3 / 5 (3) Jan 10, 2014
Oh yeah, without some revolution in engineering, you'll never get the fuel economy from a truck or car as you get from a train, plane, or boat, simply because small engines are less efficient. The reason the motorcycle gets good economy is because the vehicle is so light compared to a car, and has a much lower wind profile.

Oh yeah, turnover on diesel trains is about 50 years, give or take, but they are among the most efficient type of transport. However, that too is an apples and oranges situation. people normally don't use a diesel train unless they are going out of state, and for less populated states like Louisiana they really are very impractical as a primary means of transport.

They didn't mention what the fuel-equivalent economy was for Subway trains, as those also have an advantage: off-board power.

Other countries have off-board power for some of their above-ground trains, which works the same way the old electric trolley cars worked.
Skepticus
5 / 5 (2) Jan 10, 2014
I don't see planes stopping and starting at traffic lights, slowing for speed humps, cyclists, pedestrians. Most of the fuel is wasted to overcome inertia to cruising speed.
Milou
3 / 5 (4) Jan 10, 2014
The fault here lie within the automotive industry and there promotional strategy. They were pushing for the population to buy the biggest and best vehicle at their lowest cost (disregarding fuel or logic efficiency).

After all, we have the "terminator" pushing to have all of us buy the Hummer. Then we had congress make this purchase a business vehicle tax deduction. All courtesy of GM. With Ford it was "your not a man without a big contractor's style truck". Prius was for Wimps.

Hopefully the market will change this corporate behavior???
Eikka
5 / 5 (1) Jan 10, 2014
without some revolution in engineering, you'll never get the fuel economy from a truck or car as you get from a train, plane, or boat, simply because small engines are less efficient.


This is less of a matter of technical efficiency and more about social efficiency, because trains and planes, and public transportation in general gets worse efficiency per passenger mile if they attempt to serve as many customers and as many routes as private vehicles.

So the reason they do get good efficiency is because they shuttle between A and B, while the people travelling by them are actually going to and from A and B to C,D,E,F,G... in a car.

tadchem
5 / 5 (1) Jan 10, 2014
"Fuel economy" is not the only consideration. The traveler also must consider costs and time. I recently took a 900 mile trip by air: Ticket cost $350, time 12 hours (including layover, clearing TSA, early arrival to deal with luggage). The same trip in my car (a 30 mpg Honda Civic) would have cost me $120 in fuels costs, but 16 hours of driving time. The 4 hours difference cost me $230.
antialias_physorg
5 / 5 (2) Jan 10, 2014
would have cost me $120 in fuels costs

Fuel costs aren't the only costs you're paying. Depreciation and maintenance have to be figured in (which account for more than double the fuel cost if you look at tax deductions you can take on miles travelled to/from work...at least over here).
Those are already included in the price of your plane ticket.
Eikka
5 / 5 (2) Jan 10, 2014
Depreciation and maintenance have to be figured in


Not all of them, because you still own the car whether or not you take the plane.

In fact, the less you use the car the more expensive the other miles are because you're paying insurance and depreceation while it's standing in your garage being no use to you.
VENDItardE
1 / 5 (1) Jan 10, 2014
.this comparison is absurd, I can't remember the last time I took a plane or train to work or the grocery store or a movie or a bar or the cleaners or ...................
Egleton
not rated yet Jan 10, 2014
How about 80 MPG?
http://www.youtub...1ZGi1bTQ
It is all about the inertia and the co-efficient of drag.
And about what the public will buy. And what are they interested in? The shape of the headlights.
Vote with your wallet.
rwinners
not rated yet Jan 11, 2014
I don't see a valid comparison. Planes travel hundreds or thousands of miles at high speed. Trains will you some places at a much slower pace. Neither will get you to the local grocery or pharmacy or doctors office.
HeloMenelo
not rated yet Jan 11, 2014
What we need is for ELECTRICS to take over.... No engine maintenance, No engine OIL no FUEL. I can see however we are not quit in control of if and when it would happen though..... If only someone can break through the sour grip big oil has on the world.
ryggesogn2
1 / 5 (4) Jan 11, 2014
the sour grip

It's called physics and economics.
Skepticus
1 / 5 (2) Jan 11, 2014
the sour grip

It's called bureaucRATS' lobbied (bribing by law) and directed politics
ryggesogn2
1 / 5 (3) Jan 11, 2014
the sour grip

It's called bureaucRATS' lobbied (bribing by law) and directed politics

It's called cost per unit energy density.
Newbeak
not rated yet Jan 11, 2014
Here's what's needed:http://www.lowtec...les.html