Table 3
Comparison of NHTS Trip Estimates to Other Travel Data
| Monthly average pre-9/11 period (Mar. 2001-Sept. 11 2001) | Monthly average post-9/11 period (Sept. 12, 2001 - May 2002) | Percent change | |
|---|---|---|---|
| Vehicle Miles Traveled | |||
| Actual | 242.3 | 225.1 | -7.1 |
| Forecast in absence of 9/11 | 242.3 | 225 | -7.2 |
| NHTS Personal Vehicle Trips (millions.) | |||
| Estimated | 201.8 | 181.2 | -10.2 |
| Air RPM (millions.) | |||
| Actual | 63.1 | 46.4 | -26.4 |
| Forecast in absence of 9/11 | 63.1 | 58.1 | -7.8 |
| NHTS Air Trips (millions) | |||
| Estimated | 18 | 14.1 | -21.7 |
| Rail RPM (millions.) | |||
| Actual | 508.3 | 439.1 | -13.6 |
| Forecast in absence of 9/11 | 508.3 | 436.4 | -14.1 |
| NHTS Train Trips (millions.) | |||
| Estimated | 1.7 | 1.6 | -5.5 |
| NHTS Bus Trips (millions.) | |||
| Estimated | 5.1 | 4.5 | -12.1 |
SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics.
NOTE: Shaded difference not significant at a 0.05 level. Pre- and Post-9/11 monthly estimates of VMT are prorated for the NHTS survey overlap months of March, April, and May 2001 and 2002, using NHTS pre-and post-9/11 datasets. The weights for the overlap months are calculated using the proportion of trips taken in those months from the pre-and post-9/11 datasets. September 2001 is prorated using 0.33 for the pre-9/11 weight, and 0.67 for the post-9/11 weight.