Excess Automobile Deaths as a Result of 9/11

People commented about a point I made in a recent essay:

In the months after 9/11, so many people chose to drive instead of fly that the resulting deaths dwarfed the deaths from the terrorist attack itself, because cars are much more dangerous than airplanes.

Yes, that’s wrong. Where I said “months,” I should have said “years.”

I got the sound bite from John Mueller and Mark G. Stewart’s book, Terror, Security, and Money. This is footnote 19 from Chapter 1:

The inconvenience of extra passenger screening and added costs at airports after 9/11 cause many short-haul passengers to drive to their destination instead, and, since airline travel is far safer than car travel, this has led to an increase of 500 U.S. traffic fatalities per year. Using DHS-mandated value of statistical life at $6.5 million, this equates to a loss of $3.2 billion per year, or $32 billion over the period 2002 to 2011 (Blalock et al. 2007).

The authors make the same point in this earlier (and shorter) essay:

Increased delays and added costs at U.S. airports due to new security procedures provide incentive for many short-haul passengers to drive to their destination rather than flying, and, since driving is far riskier than air travel, the extra automobile traffic generated has been estimated in one study to result in 500 or more extra road fatalities per year.

The references are:

Garrick Blalock, Vrinda Kadiyali, and Daniel H. Simon. 2007. “The Impact of Post-9/11 Airport Security Measures on the Demand for Air Travel.” Journal of Law and Economics 50(4) November: 731­–755.

50(4) November: 731­–755. Garrick Blalock, Vrinda Kadiyali, and Daniel H. Simon. 2009. “Driving Fatalities after 9/11: A Hidden Cost of Terrorism.” Applied Economics 41(14): 1717­–1729.

Business Week makes the same point here.

There’s also this reference:

Michael Sivak and Michael J. Flannagan. 2004. “Consequences for road traffic fatalities of the reduction in flying following September 11, 2001.” Transportation Research Part F: Traffic Psychology and Behavior 7 (4).

Abstract: Gigerenzer (Gigerenzer, G. (2004). Dread risk, September 11, and fatal traffic accidents. Psychological Science, 15 , 286­287) argued that the increased fear of flying in the U.S. after September 11 resulted in a partial shift from flying to driving on rural interstate highways, with a consequent increase of 353 road traffic fatalities for October through December 2001. We reevaluated the consequences of September 11 by utilizing the trends in road traffic fatalities from 2000 to 2001 for January through August. We also examined which road types and traffic participants contributed most to the increased road fatalities. We conclude that (1) the partial modal shift after September 11 resulted in 1018 additional road fatalities for the three months in question, which is substantially more than estimated by Gigerenzer, (2) the major part of the increased toll occurred on local roads, arguing against a simple modal shift from flying to driving to the same destinations, (3) driver fatalities did not increase more than in proportion to passenger fatalities, and (4) pedestrians and bicyclists bore a disproportionate share of the increased fatalities.

This is another analysis.

Posted on September 9, 2013 at 6:20 AM • 42 Comments