Possible Insight

More Environmental Tradeoffs

with 4 comments

The Corporate Average Fuel Economy (CAFE) standards will rise from 27.5 mpg to 35 mpg from now until 2020. That should decrease any pollutant associated with burning fossils fuels.  All good, right?  Wrong.

There is a trade off in safety.  You are much more likely to die in a small car. The WSJ Online reports on a recent Insurance Insititute for Highway Safety (IIHS) study that shows  small cars like the Honda Fit and Toyota Yaris fair very poorly in two-car frontal offset crash tests against the Honda Accord and Toyota Camry. This is against mid-sized cars from the same manufacturer, so a reasonable comparison.

The higher-level statistics are a bit frightening.  According to the same IIHS study, the death rate for mini cars is twice as high in multi-vehicle collisions as that for very large cars.  Even in single car crashes and compared to a mid-sized car, the death rate is 17% higher.

This NHTSA study presents a model of vehicle weight and safety. For every 100 lbs you reduce the weight of a light car, you increase the death reate by 5.63%. That means the reduction of weight targeted at improved mileage accounted for 13,608 additional fatalities from 1996 to 1999 in the light car class.  Across the light car, heavier car, and light truck classes, the increase was 39,197 fatalities.

A USA Today analysis of crash data since CAFE went into effect estimates that for every mile per gallon improvement, you get an extra 7,700 fatalities (sorry, there doesn’t seem to be an original copy of the article online: James R. Healey, “Death by the Gallon,” USA Today, July 2, 1999).

According to this NHTSA data, there were 29,039 automobile fatilities for men in 2007.  According to this CDC fact sheet, 322,841 men died from heart disease in 2007.  So you should still devote more effort to your cardiac-related lifestyle.  But I don’t know of any lifestyle interventions that will cut your heart attack risk by 50% (other than stopping smoking).

The Tesla Model S will supposedly weigh 3825lbs with the largest battery pack.  That’s a little heavier than the Toyota Camry’s 3483lbs. Whew! At least there may be a potentially safe and efficient alternative.


Written by Kevin

April 18, 2009 at 3:08 pm

4 Responses

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  1. What do you think of the cash for clunker movement? I’m concerned that if you have a car with a 10 year life left on it that the extra emissions from it’s continued use may be less than the emissions/water use required to mine metals, develop paints, make batteries etc and construct the alternative car.


    April 20, 2009 at 5:07 pm

  2. It depends on how clunky the clunker is. A 35 year old Oldsmobile boat or a 20 year old Toyota?

    There’s a really steep emissions improvement curve from the early 70s to early 90s models.

    I think the resale value is a good indicator here. If you can get a clunker for under $500, it’s probably an environmental win.


    April 20, 2009 at 6:47 pm

  3. I wonder if cash for clunkers will become a hidden tax on the poor. Let’s say the cash back from the gov’t for buying a hybrid is $5,000. So if I don’t own a clunker but will be buying an eligible car I will be in the market for a clunker and competing against a person who can only afford a clunker. Eventually as fewer clunkers are available the price will approach the incentive amount less some factor for annoyance of having to buy and then give it to the gov’t. So a clunker that would have gone for $500 will be trading at $4500…


    April 22, 2009 at 9:41 am

  4. 1) Just found your blog. Good work!

    2) Couldn’t this be seen as an externality based on the weight of your car? We could deal with this by pricing in the externality – or, in more concrete terms, requring that liability insurance be higher for bigger vehicles to cover the increased damages when you hit something (assuming it’s your fault).

    (Yes, I know I’m poking an old discussion. But it’s not that old…)

    Chris S

    June 2, 2009 at 12:31 pm

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