In 1997, the Federal Highway Administration conducted a study of truck user tax equity, called the “Highway Cost Allocation Study.”[37] The study was updated in 2000. The study found that tractor-trailer combination trucks in the 80,000 pound GVW category range pay about 80 percent of the costs they impose. For even heavier capacity trucks, in the 100,000-pound GVW category and up, however, they found that trucks pay just 40 percent of costs incurred by the federal government on their behalf. On the other hand, for trucks under 50,000 pounds GVW, the study found that trucks paid 140 percent of their fair costs. Overall, this data would suggest that trucks pay a significant share of the costs they impose, but that, at least at the typical 80,000 pound tractor-trailer level, that not all costs are covered.

The above studies estimated that trucks may be responsible for up to 40 percent of the costs to design, build and repair the roads they travel on. In Michigan, in 2000, trucks were estimated to pay 16 percent of the monies going into the MTF.[38] This information, and the fact that Michigan ranks very low among the states in total truck taxation, would suggest that Michigan trucks are not yet paying their fair share of road costs.