Figure 5 compares equity ratios estimated in this study for various vehicle classes in 2000 with equity ratios estimated in the 1982 Federal HCAS.
Much of the change in equity ratios for single-unit trucks is attributable to changes in federal highway user fees enacted in 1982 following the 1982 Federal HCAS.
Estimates of air pollution costs reflecting the latest research by the Environmental Protection Agency could not be completed in time to be included in the 1997 HCAS but will be included in a subsequent addendum.
Many factors affecting the equity and efficiency of the highway user-fee structure changed since the 1982 Federal HCAS.
Table 6 summarizes the key findings of the 1997 Federal HCAS.
Table 6 - Summary of Key Findings in the 1997 Federal HCAS
In this study, as in previous federal HCASs, highway-user fees paid into the Federal Highway Trust Fund (HTF) by different vehicle classes were compared to HTF expenditures for pavement, bridge, and other highway-related improvements attributable to each vehicle class.
The linkage between highway user fees and highway program costs is central to HCASs, which seek to determine whether fees paid by each vehicle class cover infrastructure and other transportation agency costs caused by those vehicles.