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.
Vaclav Smil (2015) “Cars Weigh Too Much” Spectrum, IEEE vol.52, no.1, pp.24,24 doi: 10.1109/MSPEC.2015.6995626