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Updated 1:30 PM November 24, 2004




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Roadway deaths up after 9/11 due largely to local driving

Though Americans may have been skittish about flying in the aftermath of 9/11, new research shows that driving on the nation's roadways was certainly no safer.

In the three months following the attacks, there were 1,018 more traffic fatalities than projected based on trends for earlier months in 2000 and 2001—9 percent more deaths than expected.

Furthermore, the largest increase occurred on local roads, not interstate highways that would be the main alternative to flying. Local roads, both urban and rural, accounted for 45 percent of the increase in traffic deaths.

"This suggests that a substantial proportion of the people who decided not to fly after Sept. 11 did not drive to the destination they originally intended, but instead increased local, short-trip driving," says Michael Sivak of the U-M Transportation Research Institute (UMTRI).

Estimates indicate that for the last three months of 2001, compared with 2000, there was an increase of 4 percent in miles traveled on rural interstates over what would have been expected based on January to August trends for these two years, say Sivak and UMTRI colleague Michael Flannagan. Fatalities on these roads, however, increased by just 1 percent more than expected.

"It may be that those who did replace flying with a trip on rural interstates to their original destination—perhaps middle-aged business people—were less risky than the average driver, as middle-aged business people would tend to be," Flannagan says.

Sivak and Flannagan also found no increase in driver fatalities in relation to passenger deaths, suggesting that a large portion of flights not taken—possibly business trips—were not replaced by solo road trips to the same destination, but by leisure road trips with multiple passengers, such as family members, similar to typical driving across the nation.

Finally, the researchers found that pedestrians and bicyclists bore a disproportionate share of the increased road fatalities following 9/11.

"This is consistent with the increase in fatalities primarily on local roads and provides further evidence against a simple shift from flying to driving on rural interstates," Sivak says.

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