About 21,500 motor carriers pay the Oregon weight-mile tax, including 8,500 Oregon-based carriers and 13,000 outof- state carriers with trucks operating in Oregon. When they register a truck they pay a registration fee that is based on the truck’s highest combined weight for the year (weight of the truck plus maximum weight of the load it will haul). Their weight-mile tax is then based on the declared combined weight(s) established for each truck combination – the heaviest weight at which the motor carrier declares the combination will operate during a month or quarter tax reporting period. A check of 283,145 trucks registered in July 2010 showed eight of every ten (225,742 total) operate at just one declared combined weight (80,000 pounds for most). Only 20% of all trucks operate under more than one declared weight. Oregon first enacted a ton-mile tax on trucks in 1925 and replaced that with a weightmile tax in 1947. In 1990, it implemented the first axle-based weight-mile tax for trucks over 80,000 pounds (Table B). Over the years, weight-mile rates have been adjusted 14 times based on the results of updated cost responsibility calculations in Oregon Highway Cost Allocation Studies.

A fuel tax liability is created when the amount of fuel consumed is larger than the amount of fuel purchased in a particular state during any one-tax quarter. If the state charges a fuel surcharge over and above the specific fuel tax levied, it will generally be charged on the total amount of fuel consumed within that state during that same quarter regardless of the amount of fuel purchased within that same state. Anytime there is more fuel purchased than consumed in a particular state during a tax quarter a fuel tax credit is created and is used to offset any fuel tax liability during that same quarter.