About 21,500 motor carriers pay the Oregon weight-mile tax, including 8,500 Oregon-based carriers and 13,000 out of- 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 weight mile tax in 1947. In 1990, it implemented the first axle-based weight-mile tax for trucks over 80,000 pounds. 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.
Today, Oregon is the only state that charges heavy trucks (over 26,000 pounds) a weight-mile tax and no diesel fuel tax. Three other states — Kentucky, New Mexico, New York — have a weight-mile tax that they charge certain heavy trucks, but also in conjunction with a diesel fuel tax and other truck fees.