How To Boost Efficiency: Lighter Cars That Carry More People

Efficiency is a many-splendored thing, and cutting vehicle weight has multiple beneficial effects.

A lighter car requires less energy to move, meaning engine output can be lower.

This, in turn, requires smaller, lighter powertrain components--which require less-beefy suspensions, further reducing weight. And so on.

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A recent article from IEEE Spectrum argues that vehicles still weigh far too much--and it analyzes vehicle-to-passenger weight ratios over history to make the case.

A Ford Model T from 100 years ago had a vehicle-to-passenger weight ratio of 7.7, it says, about the same as today's Japanese bullet trains.

But the full list of 10 examples spans more than two orders of magnitude.

Best is the bicycle: If a lightweight model weighs 15 pounds, it has a vehicle-to-passenger weight ratio of 0.1.

At the other end of the scale is the huge, gaudy, almost-19-foot-long 2015 Cadillac Escalade EXT, which features a ratio of 39 with a single 150-pound occupant.

Author Vaclav Smil urges that each vehicle carry more people--something that 70 years of dispersed U.S. suburban zoning works against.

And he explains why the ratio has increased over the last century.

"Cars got heavy," he writes, "because part of the world got rich and drivers got coddled."

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"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."

A study done more than five years ago at the University of California--Davis looked at improvements in engine efficiency from 1980 to 2005.

That study, Automobiles on Steroids: Product Attribute Trade-Offs and Technological Progress in the Automobile Sector, concluded that only 15 percent of those improvements had gone toward boosting fuel efficiency.