Transportation safety in the United States

Transportation safety has steadily improved in the United States for many decades. Between 1920 and 2000, the rate of fatal automobile accidents per vehicle-mile decreased by a factor of about 17. Except for a pause during the 1960s, progress in reducing fatal accidents has been steady. Safety for other types of U.S. passenger transportation has also improved substantially, but long-term statistical data are not as readily available. While the fatality rate roughly leveled off from 2000 to 2005 at around 1.5 fatalities per 100 million miles traveled, it has resumed a downward trend to 1.27 in 2008.

Following an approach used by several writers, one can compare the likelihood of a fatal accident while driving and while flying with a scheduled airline. This is most meaningful for trips in which either mode of transportation is a reasonable alternative. For the U.S., a typical trip of this sort is from the Boston, MA, area to the Washington, DC, area, about 6 hours door-to-door by air travel and 7 hours door-to-door by automobile. To compare typical risks, one can use the U.S. average fatal automobile accident rate of 1.5 per 100 million vehicle-miles for 2000 and the U.S. average fatal scheduled airline accident rate of 0.18 per million flight segments for 1995-2005:

Risk estimation               By air   By auto Flight segments                  1        0 Risk (millionths)                0.2      0 Miles driven                    40      450 Risk (millionths)                0.6      6.8 Total risk (millionths)          0.8      6.8

The likelihood of a fatal accident, estimated for this trip (assuming a total of 40 miles driven to and from the airports), is more than eight times greater when driving all of the way than when flying. As shown in this example, the largest part of the risk of flying is the risk incurred driving to and from airports (0.6 while driving to/from the airport vs. 0.2 for the flight itself).