Although trucks pay significant taxes, and there have been large percentage increases
over the last ten years, they still do not pay their full share of costs. However, the
rate of underpayment is considerably smaller than most of the public believes, and in some
states trucks are paying more than their share of estimated costs. Two federal studies
have been conducted on this issue since 1982.17 The first of these two studies
was done in 1982 by the Federal Highway Administration (FHWA), and was based on 1977 data.
That study found that five axle tractor-trailer combination trucks were paying 68% of
their cost responsibility on federal aid highways. In response, federal truck taxes were
increased 231% on a combination of fuel, truck and trailer excise sales tax, federal use
tax, and tire tax. A 1987 study by the FHWA found that five axle trucks weighing between
70,000 and 80,000 pounds were paying 86% of their costs. In response, federal fuel taxes
were increased 5 cents in 1990 and another 4.5 cents in 1993, although not all of the
funds were committed to the Highway Trust Fund. FHWA is conducting a new cost allocation
study for release in about two years.
Fifteen states have conducted their own cost allocation studies since 198618
The average finding was that five axle tractor-trailer trucks were paying 96% of their
cost responsibility. Based on a review of these states' total fuel taxes, but not
considering registration fees, the average fuel tax was 23.6 cents per gallon including
sales taxes and surcharges. Michigan's effective rate of 15.0 cents per gallon would be
61.4% of these other states' fuel taxes. Without any consideration of registration fees
one might conclude that Michigan trucks are paying about 60% of imposed costs. This rough
estimate may indicate of the magnitude of Michigan's truck underpayment problem.