1 For air carriers, the data were dampened, or smoothed, to reduce the month-to-month fluctuations. This dampening was performed using an exponential smoothing model, with a weight of 0.95. Departure data, and hence the denominator of the rates, are not strictly comparable between pre- and post-1977 eras.
SOURCES: 1975-2000-Various sources, as cited in U.S. Department of Transportation,
Bureau of Transportation Statistics, National Transportation Statistics 2001,
available at http://www.bts.gov.
2000-Aviation: National Transportation Safety Board, Aviation Accident Statistics, available at http://www.ntsb.gov/aviation/stats.htm, as of Oct. 2, 2002.
Highway: U.S. Department of Transportation, National Highway Traffic Safety Administration, Traffic Safety Fact Sheet 2000: Overview, DOT HS 809 329, (Washington, DC: 2001), table 1; and personal communication, Nov. 1, 2002.