| Characteristic | 1965 Survey | 1981 Survey | 1990 Survey | Percent Change
1965 - 1990 |
|---|---|---|---|---|
| Vehicles Available | 1,941,600 | 3,349,700 | 4,020,100 | 107% |
| Vehicle Trips | 6,288,000 | 10,307,000 | 10,914,300 | 74% |
| Vehicle Hours of Travel | 1,928,300 | 3,093,200 | 3,738,000 | 94% |
| Average Trip Duration (min.) | 18.4 | 18.0 | 20.5 | 12% |
| Vehicle Hours of Travel / Vehicle | 0.99 | 0.92 | 0.93 | -6% |
| Vehicle Trips / Vehicle | 3.24 | 3.08 | 2.71 | -16% |