Note: The Nationwide Personal Transportation Survey (NPTS) was first conducted in 1969, and then again in 1977, 1983, 1990, and 1995. Numerous methodological improvements in the NPTS make exact comparisons across time difficult, but travel behavior for these two points in time are adequately (if not perfectly) reflected in the survey data.
Source: U.S. Department of Transportation, Federal Highway
Administration, 1995 Nationwide Personal Transportation
Survey data (Washington, DC: 2000), available at
www-cta.ornl.gov/npts, as of October 2000.