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Vaclav Smil: Cars weigh too much

In an opinion piece in the January 2015 issue of IEEE Spectrum, Vaclav Smil, Distinguished Professor Emeritus at the University of Manitoba, Fellow of the Royal Society of Canada (Science Academy), and the Member of the Order of Canada, writes that modern cars—even with the tremendous gains in efficiency and even electrics—simply weigh too much, given the dominant usage pattern of one driver per vehicle.

Data on commuting from the US Census Bureau show that in 2012, 76% of Americans drove to work alone; carpooling was down from 20% in 1980 to 12%; and the use of public transportation was down from 6% to 5%.

And so the outlook is for ever-better engines or electric motors in heavy vehicles used in a way that results in the worst weight-to-payload ratios for any mechanized means of personal transportation in history.

—Vaclav Smil

Smil notes that despite a 92% increase in the power-to-weight ratio of engines from the Model T (1 watt from 12 grams) to the average modern car today (1 watt from 1 gram), the mass of the vehicles themselves has tripled.

And because more than three-quarters of US commuters drive alone, you get the worst ratio of vehicle-to-passenger weight since a mahout last rode a bull elephant to work.

—Vaclav Smil

Despite advances in lightweighting, the vehicle-to-passenger weight ratio is what ultimately limits energy efficiency, Smil argues. Assuming a 70 kg passenger, a 7 kg bicycle has a weight ratio of 0.1; a modern bus, 5 or less; the Model T, 7.7; a Toyota Camry, 20; the F-150, 32.

Of course, you can get quite spectacular ratios by pairing the right car with the right driver. I regularly see a woman driving a Hummer 2 that easily weighs 50 times as much as she does. That’s like going after a fly with a steam shovel.

… Cars got heavy because part of the world got rich and drivers got coddled. Light-duty vehicles are larger, and they come equipped with more features, including automatic transmissions, air conditioning, entertainment and communication systems, and an increasing number of servomotors. And new battery-heavy hybrid drives and electric cars will not be lighter: The small all-electric Ford Focus weighs 1.7 metric tons, General Motors’ Volt is more than 1.7 metric tons, and the Tesla is just above 2.1 metric tons.

—Vaclav Smil

Smil has spent his career working on energy and its interactions with the environment, economy and food production and its impact on the quality of life and political and strategic matters. He has published 35 books and more than 400 papers on these topics.




A lot of the weight increase is due to mandated safety equipment; today's Golf is more than 1000 lbs heavier than the first one I owned.  If the law requires such weight, there's no way for the consumer to push back.


Before anyone points out that this is obvious to virtually everyone over the age of 5 (except maybe in academia), we must wish Smil full reentry into the sentient world, from wherever he’s been.

Also – a few facts to speed his reentry:

Airplane mode will not make your phone fly.

Food is a cure for hunger.

Sandwiches are not made with sand.

People who have the most birthdays tend to be the oldest and live the longest.

If your parents didn't have kids chances are you won't either.

Jim McLaughlin

My Think City EV weighs 1.066 metric tonnes. But when it is power by nuclear fusion via PV solar panels, what difference does it make?


I must strongly protest.
Consumers want the bells and whistles,3 motor electric memory seats with inbuilt wake up alarms inebriate lockouts and body bass booster.Try lifting those thru the door space.
I know - it took two people and one was permanently incapacitated with herniated discs.
How was that ever a safety device?

Hepa filters that claim to remove 90% of pollutants? when stuck in trafffic. But fail to mention that new car salemen have ~10 times the rate of liver cancer.

Throw the aircon over the left shoulder and open the window. Don't sit in traffic jams.This would save several hundred pounds and bonus near infinite tanks of fuel. (unless we are driving e).

There are only two safety considerations:

Primary; windscreen or visibility, brakes, tyres, steering etc under ergonomics. These also benefit from lightweighting.
If an 8088 cpu can land man safely on the moon, a smartphone should get us safely to the end of the universe (with a little help from Stephen Hawkins.)

Secondary; Seatbelts,Airbags, crumple structure, coffecup holder.

Case in point.
125kg mcycle 70hp accelerates from other traffic,avoids obstacles - travels as well on the back wheel as the front.(lands lightly so easy to control)
Makes enough ruckus to keep the road ahead clear.(ambo's, police cars haded for Macdonalds etc) Take some baffling out and save a bit more weight. No pillion option save more weight.
Combined with a CO2 inflation suit smart phone connected to emergency response sevices.Or something along this line.

@ T.T.
Bit hard to argue with that. (All people over 65 should be euthanised at birth - goes up incrementally year on year)


@ Jim,
Try removing half the depleted uranium and put the rest inside the space provided behind front bumper. That should give added protection from foolish train drivers forgetting to stop at crossings.


The gentleman from Manitoba to put it politely has his cranium inserted between the cheeks of his own maximus gluteus.

Today's lone driver move his 1.7 metric ton vehicle between his origin to his destination with less energy consumption than virtually all18th century tech 'mass transit'.

The difference is the route between origin and destination. Mass Transit travels on pre-defined routes f,far from the optimum route for the individual travelor from suburb near to origin to center city and then a transfer can be affected to another such that will take the traveler near his destination.

Together with a massive and profligate use of energy and waste of time.

It doesn't take much to show how inefficient such obsolete technology truly is.

Roger Pham

Why are cars getting bigger and consequently heavier?

Simple: People want the protection from the hefty mass of a bigger car. Then it became an arm race: those in small cars feel threatened by behemoth SUV's, so, will save hard to be able to afford SUV's...

How to solve this problem?
Simple: Put all those menacing SUV's and other large cars on diet to shed their weight gradually, perhaps by 100 # less for subsequent model years, until they will come down to weigh comparable to a typical 3000-£ sedan. So, either SUV's or vans or large sedans will be made more and more out of aluminum or CF, like Ford has done, with smaller blown engines like Ford has done... or cheaper SUV's and cars that can't afford aluminum and will be made smaller and made out of steel to comply to the maximum weight limit.

How to make it happen?
Simple: The government, in the name of safety and efficiency for all! The government has the power to mandate safety and fuel efficiency, and this smack within government's power.


Depending how lifetime use personal transport has averaged energy consumption approaching that needed to create same.

Of course the Motor city concept from '50s America mandates the private motor tank as a necessity.That requires further infrastructure and expensive upkeep for citizens to be able to function as members of society.

Studies show that citizenry of cities where public transport is well planned are wealthier as a result. It is implicit that wealthier citizenry choose to live in better conveniently resourced neighborhoods and the municipal managers will also have better resources to implement socially progressive programs including sports and rec, hospitals and medical, education etc etc.

Car share strategies are also of economic value while often offering easy (some free) parking options while gaining maximum life use from up to date vehicle technology.

Mass transit frees up municipal funds for more pressing infrastructure as well as space for urban parks and landscape.
Not to mention cleaner air.

Lets not compare todays futuristic 21st century technology with Watt's original alternative.

The real problem with mislocated craniums really takes off when it has become too swollen or elevated.
Makes one wonder how they can even walk?


I driven a lot of different cars in my life and small lightweight cars or motorcycles with a nice power to weight ratio drive better and are more fun to drive but all of this is compromise and art because I was in deep trouble at one time because I driven my car one particular night with 4 big man in a very small Toyota tercel and the car was working poorly without acceleration and poor breaking so much that it was dangeurous but when I drive it alone it was nice and big mpg. I dream of owing a thermoplastic car with aluminium with a small high performance engine. big mpg, dynamic ride, good breaking, aerodynamic, smooth precise ride, no rust, fast heating in winter, 100 mph possibility, nice outside view, low noise but some of it under acceleration and high speed, electronic anti-collision, pressure oil 4 engines, 200-300 mpg.


Instead of scoffing, Posters might do well to remember that what Smil is saying here is TRUE, and their intelligence would be better directed towards efforts to reverse this trend.RP may be simply being Ironic in saying that it is within Government's power to mandate lower weights, but he is certainly correct in pointing out that ownership of bigger, heavier cars is a kind of Arms Race;which many are foolishly sucked into through swallowing the popular fallacy that they are safer in the event of an accident, quite forgetting that if the other vehicle involved was also chosen for its presumed safety, then one is no better off. This fact may again be simply stating the obvious, but the poor dummy walking into a car showroom to sign up for the biggest, heaviest bruiser he can lay eyes upon is most likely not to think about the obvious, instead working upon the popular, "It won't happen to me" syndrome. A few more statistical probabilities prominently displayed in strategic positions might help him to take such possibilities into account. Does this imply that any vehicle over a ton and a half should carry government health warning stickers? That would probably be nonsensical, but some true facts about accidents involving heavy SUVs probably ought to be made more widely known, by some means or other.Since I am not a resident of the USA I do not have access to such data, but I am sure that anyone who is, can locate it if they are genuinely concerned about this trend and not just to try to put down anyone whom they see as an easy target.


There are 2 ways to look at the heavier car = safer car.
That one, and the heavier car = more dangerous car.
Thus, you could penalise someone who kills someone in a vehicle (say) < 80% of their weight.
The law would be tricky (obviously), would you pay in cash, days in jail or payment to the victim's family.
They have a law a bit like that in Holland regarding killing cyclists by motorists (the motorist is automatically to blame).

Maybe, you would just pay a weight tax which would be used to compensate the users of smaller vehicles (or their families).

Or a momentum tax (mass x velocity), paid in real time.
or a KE tax (mass x velocity^2), paid in real time.

The problem isn't really the mass of the car, it is the KE of the car. If big cars didn't drive so fast, we wouldn't have so many deaths.

Just opening up the argument.


Totally agree with Smil. Obese ICE cars should be taxed extra to provide incentive to light weighting. Ford did a good step with the Aluminum trucks.

EV's and HEV should be less taxed proportional to MPG.

There should also be mandatory higher insurance coverage for other persons injuries in accidents.

Airlines should also charge extra for obese. Why should a little kids airfare subsidize...


Good points GdB.

Private vehicles, normally used to transport 1.3 persons, do not have to weight more than 1500 lbs and mini-bus like VUS for 6 or 7 persons could be built at around 2200 lbs.

By reducing dead weight by 50%, reducing drag and rolling resistance, the average ICEVs could do 50 mpg, HEVs about 70 mpg, PHEVs about 140 mpg.

The range of most electrfied vehicles could be doubled with the same inefficient batteries.

Roger Pham

IMHO, raising taxes on heavy private vehicles won't help much, because people value their own safety too much. The rich don't mind paying more, while poor will try to cough up more money to pay for "heavy car" tax.

Instead, all the government need to do is to mandate a maximum allowable weight for passenger vehicles at say, 5000 £ initially, to be decreased by 100£ yearly down to 3000£, so that in 20 years, no passenger private vehicles is allowed to weigh more than 3000£.

This will means bigger vehicles will have to be made out of more expensive aluminum or CF, for the wealthy, while smaller vehicles can still be made out low-cost steel for the poor. This means rich owners automatically will pay more to buy big vehicles, yet, they are no more dangerous than small steel vehicles. Big but light vehicles still afford more protection due to more crumple zone to absorb the G-shock, hence still worth the extra money, and much better fuel efficiency hence much greener, though not as dangerous to smaller cars as before.

Old big and heavy vehicles will be phased out mandatorily in due time, because they will not be allowed registration renewal after certain years.

Sorry, but we have got to take public safety and environmental protection very seriously!

all the government need to do is to mandate a maximum allowable weight for passenger vehicles

This has been done.  It's why half of the US LDV market is designated "light trucks".

For those who didn't get the previous, it failed.  Miserably.

Roger Pham

"If at first you don't succeed, try and try again."
Seriously, there are many regulations regarding traffic safety such as seat belts, airbags, ABS, crash worthiness, child seat, etc...
And mandates for fuel efficiency improvement like CAFE, and emission reduction law restricting CO2 emission...

Simply setting a gradually decreasing maximum weight allowable for ALL PASSENGER non-commercial VEHICLES, including SUV's and minivans, can KILL 3 BIRDS WITH ONE STONE: Safety, Fuel Efficiency, and Emission. CAFE law puts a 2500-£ sub-compact at the mercy of a 6000-£ monster SUV. This new law will achieve SAFETY and EFFICIENCY at the same time. It will make CAFE law obsolete.

We now have the technology to make a 3000-£ large vehicle that can carry 7-9 people. We just need some legislations to make it happen.

Simply setting a gradually decreasing maximum weight allowable for ALL PASSENGER non-commercial VEHICLES, including SUV's and minivans...

... runs smack into problems of materials cost (if you force carbon-fiber bodies to meet the other requirements, cost goes through the roof) and little things like the complete unavailability of batteries light enough to make decent EVs under such restrictions.

The Tesla Model S has a sufficiently deep crumple zone to be much safer (relatively) for lighter vehicles in a frontal impact.  Since that is the actual figure of merit we're looking for, it makes no sense whatsoever to impose a hard weight ceiling.

Roger Pham

Ha, ye of little faith!
No need to use CF, though in 20 years, CF will be a lot cheaper, thanks to mass production of FCEV's fuel tanks, creating a massive market for CF. Cheaper aluminum can be used, like Ford and Tesla are using mow.

Consider the Cessna 206H with empty weight of 2200 £ and can seat 6, with useful load of 1400 £. The Lycoming IO-540 itself weighs 500 £, and in a car, can be replaced with a 2-liter engine weighing 250 £. So, an aluminum airplane with 6 seats weighing 1950 £ can be turned into an all-aluminum 6-seat car weighing around 2000 £, while an even bigger 8-9-seat car can be made to weigh under 3000 £. Windows panels can be made from acrylic with a very thin layer of Gorilla glass on the outside for scratch resistance. Wheels are alloy with low profile tires using little rubber. Suspension springs are made from fiber glass instead of steel.

The Tesla Model S weighs 4600 £ with 1300-£ battery pack. 20 yrs from now, the battery pack may weigh half as much, or 650 £. Then, one can shave off 200 £ from the frame, 150 £ from the power train, then 300-£ from the wheels, brakes, and suspension. So, 1300-£ wt saving so far, but it is not good enough, 4600 - 1300 = 3300 £. Need to lose 300 £ more. How to lose 300 £ more?
Answer: By using modular battery packs of 30-kWh each x 3 to get 350-mi range. The 650 £ battery weight is for 90-kWh. Reducing this to 30-kWh pack will shave off above 400 £, or 2900 £ for daily driving range of 120 miles. You now have a 7-seat BEV with curb wt of only 2900 £!

Right after departing for a long trip, stop by a battery rental/swapping station to rent two more packs, and while there, juiced up with 120-kW charger on your own 30-kWh pack, and you be good for 300 miles. You will only swap the two rental packs during your trip, and never swap out your own pack, just Supercharge it for about 10 minutes to put in 20-kWh!

Henry Gibson

As mentioned elsewhere, Artemis digital hydraulic pumps and motors can reduce fuel consumption to half for any private passenger vehicle for the most common uses without any other changes to engine or vehicle and at far lower costs than electric hybrids. All vehicles can be converted with no increase in weight.

Humans use hydrogen, carbon, sulphur, oxygen and nitrogen compounds for most of their foods and there is no reason that automobiles for humans cannot continue to use hydrocarbons for many uses, and some automobiles can be lightweight and use electric batteries for limited distance and have small hydrocarbon using units to expand this range rarely when needed. Ammonia is a non carbon fuel that is made from hydrogen and nitrogen of the air and can be burnt in engines or turbines or used as fertilizer or to make complex fertilizers and explosives.

No one has of yet developed a process to productively combine the oxygen in the air with the nitrogen in the air and water with the theoretically possible net production of heat. This is likely more possible than fusion of deuterium to deuterium in the short run. Deuterium to palladium fusion was likely done decades ago with the release of heat but no neutrons.

CO2 production is now the main concern of very wealthy environmentalists concerning the earth, but is not any concern at all for people living with an income of less than 50 kilowatt-hours a day; which is 99.44 percent of the earths population. California officials pretend to be concerned about CO2 and increase the fuel costs of every one in the state to maintain this pretense whilst living in extra large air conditioned houses for only one or two people and caving into uninformed demands to close nuclear power plants needing only minor non nuclear repairs.

Canada has also closed nuclear plants, but now fully ignores CO2 releases of fuel production within its borders and the CO2 released after export. This is OK. Canada can not do anything to noticeably change CO2 content of air, but neither can California, but California can buy super safe CANDU reactors from CANADA with a high tax on cheap fuel instead of enriching fossil fuel producers and others who can easily hide the total CO2 footprint of their fuels including hydrocarbon gas release, flaring, processing, transportation and heavy hydrocarbon spills on land and into water. No one can trace all of these for oil sources in foreign countries or even their own. The CANDU reactors can even be built in British Columbia and connected to AC and DC transmission lines going from the Dams on the Columbia River to California.

The Californians can pretend that all of the organic materials confined by the dams in the US and Canada are not being converted to methane and CO2 by anaerobic decomposition by organisms. And they can ignore the fact that they are using resources from outside the state that could be used by states and countries that actually contribute to the flow of the Columbia and are using fossil fuels for electric production.

The home of the KYOTO accords thinks that the Fukushima power plant failure is a good excuse to shut down all nuclear reactors in Japan, but not a good reason to depopulate permanently all locations in japan subject to Tsunami which killed at least 20000 instantly. Radiation killed no one instantly and can't be proved to have killed anyone since then. Nuclear reactors ought to be allowed to kill as many people a year as the oil and coal industries combined without great comment or shut down.

No activists favoring the closing of nuclear power plants mention that natural gas production and use in power plants releases more nuclear radiation than nuclear reactors do or have. They also never mention in their speeches that humans must and do consume radio-active elements to survive and always have even thousands of years ago even millions, and they do so every day they eat, and humans have always emitted nuclear radiation to others, but so do trees. They also do not mention that the sun and other stars and space send radio active elements into the earth's air continuously, and the suns radiations kill hundreds of people every day.

Nuclear fission reactors in the US are limited by political, not economic, reasons to use nuclear fuel at about one percent efficiency. This also increases the weight of nuclear waste by about 1000 percent. The nuclear industry may dispose of 1000 pounds of uranium for each pound it uses and some of the uranium is less radioactive than when it came out of the ground. It has been known since 1943 how to use all 1000 pounds. The use of one pound of uranium can eliminate 5 million or more pounds of CO2 going into the air and only one pound of actual radioactive waste or less is produced. The separation of radio-active elements from non radioactive elements in used reactor fuel was once forbidden in the US and is still not done because politicians kow-tow to misinformed people to get re-elected.

Nuclear reactors can produce enough energy at cheap enough prices to produce hydrocarbon or ammonia liquid fuels at prices to compete with gasoline at 2 or 3 dollars. Ammonia liquid can be stored in tanks similar to propane and used as a fuel where zero carbon vehicles require it as in range extended battery vehicles with seldom used low power range extenders. Honda produces generators that use propane cartridges and could be modified for ammonia cartridges.

Nail guns have indicated the way away from battery powered tools by using butane or propane cartridges for operating power.

Infinite fission fuel is available from minerals and the ocean. The fission of lead, if invented would produce 75 percent of the energy that the fission of uranium does. If all of the money spent on nuclear fusion had been spent on the fission of lead or gold or mercury or bismuth it might now be feasible and economic, but the fission of uranium and thorium would still be more economic. Thorium is more abundant in the earths minerals than uranium but less so in the ocean, but the already mined and purified and stored uranium "wastes" could generate all electricity needed in the US for a hundred years. Salts made from isotope separated chlorine can be used in reactors for high temperatures to chemically produce hydrogen from water. Such hydrogen can be combined with CO2 from multiple sources for automobile fuel.

Such hydrogen can be transported in steel wire reinforced aluminum lined PEX pipes at not too high of a cost to be used as home and factory fuel to replace natural gas. These homes and factories would use fuel cells or turbines as cogeneration units for electricity and heating and cooling by processes using waste heat. Organic Rankine cycles can be redesigned from geothermal units for extra electric efficiency.

Very fuel efficient Heavy water reactors can be made small in factories and use used fuel from rods now only sent to storage. Small reactors and turbines are noticeably less efficient but can be made much cheaper and use fuel that is now being wasted and energy that was lost, so efficiency is not a real issue. Large quantities of used heavy water is available and could be leased from shut down reactors or also leased from stock now in storage so that capital costs can be kept low. India produces much heavy water still. ..HG..


Hydraulic recuperation hybrids were always a good candidate for fuel saving and downsizing especially stop start applications and machines with preexisting hydraulic systems. It was simply a matter of bringing this to greater market acceptance and penetration. It is good to see that the predicted gains have been often exceeded.

When electric integration is already necessary , increasing the percentage from occasional to substantial and progressively to full electric makes economic sense.

That full utilisation of electrical power transported via wire can solve many of the problems we currently face from fossil fuel use.

There are studies showing that certain coal powered generators consume even less than half of the energy contained within, the remainder as nuclear active materials being found in the fly ash separated from the exhaust stack in the scrubbing process.

Natural gas likewise is known to contain vapors of many naturally occurring minerals that will include radioactive materials. The pumped and frack water also reflects the various minerals or elements found in the geology through which it has been in contact. Here that it at dangerous levels (common) the produced water and gas will also contain these at above legislated percent in relation to their ground concentration.

Fusion as proposed on earth is shown to occur at 120 X 10^6 o K
And experimental studies are showing temps approaching 3 million.
There are reports of positive power being achieved but the researchers suggest we are several generations from seeing sustained reactions.
possibly ~ 2050.

As with CO2 producing power generation, there are many associated known environmental as well as social costs with these methods.

Remember that the universal adoption of Industrial power generation via fossil fuels esp coal is only ~100 years old James Watt 1736 - 1819 e generation 1820s and early 1830s by the British scientist Michael Faraday. We are already at a point where continuing down this path is considered as extremely dangerous to our very existence.

For lack of time, I hope some of your concerns have been addressed.


Various temperatures seen in experimental fusion quoted range from 10 thru 30 to 100 million degrees.


Fusion, schmusion. The particle emissions will render the reactor a piece of hot radioactive waste, and in the end the energy you derive is akin to boiled water.

And yes, cars weigh too much, your roads being proof. 1960's 20K lb. vehicles have effectively been banned from the roads for tearing them up, and your SUV's are doing the same thing in slow motion. There are automated means of effectively laser printing sealant over cracks, and closing the seams between asphalt strips, but there is no interest. Gravel, ground glass, and rubber can be graded and paved on points where varying degrees of wear occur, but no one cares. Pre-stressing cement with steel springs and coating the surface with permeating resin is known, but apparently not by our genius municipalities. Those potholes are also largely the result of the wrong, badly dispersed, and too much road salt. I'll have much to say.

Take care of these roads and we can all drive dymaxion cars. 3 wheels, less drag,better distribution of weight along the width of the road surface.

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